How to Deal with Skin Biopsy in an Infant with Blisters?

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Review How to Deal with Skin Biopsy in an Infant with Blisters?

Stéphanie Leclerc-Mercier

Reference Center for Genodermatoses (MAGEC Center), Department of Pathology, Necker-Enfants Malades Hospital, Paris Centre University, 75015 Paris, France; [email protected]

Abstract: The onset of blisters in a neonate or an infant is often a source of great concern for both parents and physicians. A blistering rash can reveal a wide range of diseases with various backgrounds (infectious, genetic, autoimmune, drug-related, traumatic, etc.), so the challenge for the dermatologist and the pediatrician is to quickly determine the etiology, between benign causes and life-threatening disorders, for a better management of the patient. Clinical presentation can provide orientation for the diagnosis, but skin biopsy is often necessary in determining the cause of blister formations. In this article, we will provide information on the skin biopsy technique and discuss the clinical orientation in the case of a neonate or infant with a blistering eruption, with a focus on the histology for each etiology.

Keywords: blistering eruption; infant; skin biopsy; genodermatosis; SSSS; hereditary epidermolysis bullosa; keratinopathic ichthyosis; incontinentia pigmenti; mastocytosis; auto-immune blistering diseases

1. Introduction The onset of blisters in a neonate or an infant (<2 years old) is a source of great concern for both parents and physicians. Therefore, a precise diagnosis, between benign causes and Citation: Leclerc-Mercier, S. How to life-threatening disorders, is quickly needed for the best management of the baby. Deal with Skin Biopsy in an Infant Several diseases with various backgrounds (infectious, genetic, autoimmune, drug- with Blisters? Dermatopathology 2021, related, traumatic, etc.) can lead to a blistering eruption. 8, 159–175. https://doi.org/10.3390/ Skin biopsy is often necessary in determining the cause of the blister formation. dermatopathology8020022 In the present article, only the most frequent etiologies speciﬁc to this age group will be described, with a special emphasis on histology in the clinical context (Table1). Academic Editor: Gürkan Kaya

Table 1. Most frequent blistering disorders in neonates and infants. Received: 3 May 2021 Accepted: 1 June 2021 Staphylococcal scalded skin syndrome Published: 4 June 2021 Infections Impetigo Scabies Publisher’s Note: MDPI stays neutral Hereditary epidermolysis bullosa with regard to jurisdictional claims in Genodermatosis Keratinopathic ichthyosis published maps and institutional afﬁl- Incontinentia pigmenti iations. Mastocytosis Cell proliferation Langerhans cell histiocytosis Autoimmune blistering diseases Bullous pemphigoid and others Drug reactions SJS, TEN, etc. Copyright: © 2021 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article Vesicular and pustular eruptions will not be discussed in this review. distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Dermatopathology 2021, 8, 159–175. https://doi.org/10.3390/dermatopathology8020022 https://www.mdpi.com/journal/dermatopathology DermatopathologyDermatopathology2021 2021, 8, 8, 1602

1.1.1.1. How How Can Can the the Clinical Clinical Context Context Provide Provide Information Information Concerning Concerning the the Etiology? Etiology? TheThe underlying underlying context context of of blistering blistering lesions lesions in in newborns newborns or infantsor infants will will sometimes sometimes be helpfulbe helpful to provide to provide a clinical a clinical orientation. orientation. Some Some elements elements important important to investigate to investigate are listed are belowlisted withbelow examples with examples of etiology: of etiology: -‐ distributiondistribution of of the the lesions: lesions: localized localized blisters blisters (traumatic/suction (traumatic/suction blister,blister, local local infection, infection, solitarysolitary mastocytosis, mastocytosis, etc.) etc.) -‐ generalgeneral symptoms:symptoms: fever,fever, systemicsystemic disordersdisorders (infection,(infection, toxictoxic epidermalepidermal necrosis,necrosis, metabolicmetabolic disorder, disorder, etc.) etc.) -‐ tensetense or or ﬂaccid flaccid blister/erosion blister/erosion (giving(giving indicationsindications onon thethe levellevel ofof splitting)splitting)

1.2.1.2. What What Is Is the the Appropriate Appropriate Technique Technique for for Skin Skin Biopsy Biopsy in in This This Context? Context? EvenEven if if invasive, invasive, a a skin skin biopsy biopsy is is often often necessary necessary in in this this situation situation for for a a quick quick diagnosis diagnosis andand a a better better management management of of the the patient. patient. TheThe physician physician should should give give the the pathologist pathologist a a precise precise report report with with the the clinical clinical data, data, the the preciseprecise topography topography of of the the biopsy, biopsy, the the anesthetic anesthetic procedure, procedure, and and a a description description of of the the lesion lesion collected.collected. TheThe injectioninjection ofof anan anestheticanesthetic productproduct willwill bebe performed, performed, butbut an an anesthetic anesthetic creamcream containing containing lidocaine lidocaine prilocaineprilocaine shouldshould notnot be be applied applied prior prior to to the the biopsy biopsy since since it it cancan be be responsible responsible for for histopathologic histopathologic changes changes and and lead lead to to misdiagnosis, misdiagnosis, and and also also prevent prevent ultrastructuralultrastructural analysis analysis (vacuolization (vacuolization of of keratinocytes) keratinocytes) [ 1[1].]. AA skinskin biopsybiopsy will be taken taken for for routine routine examination, examination, and and another another will will be be frozen frozen for forimmunohistochemistry immunohistochemistry techniques techniques (split (split skin skin is not is usually not usually performed performed in this in acute this acute situa‐ situation).tion). A biopsy A biopsy for forelectron electron microscopy microscopy is isusually usually not not routinely routinely available butbut couldcould be be usefuluseful for for genodermatosis genodermatosis diagnosis. diagnosis. TheThe biopsy biopsy should should be be taken taken on on the the most most recent recent lesion lesion within within 24 24 h h (and (and within within 12 12 h h whenwhen possible): possible): •  forfor routine routine histology, histology, it it must must be be performed performed between between the the normal normal skin skin and and the the edge edge of theof the blister blister so that so that the the epidermis epidermis does does not not detach detach as in as Figure in Figure1, fixed 1, fixed in formalin, in formalin, and processed routinely (paraffin embedded, haematoxylin and eosin (HE) staining) in and processed routinely (paraffin embedded, haematoxylin and eosin (HE) stain‐ order to determine the anatomic level of the blister ing) in order to determine the anatomic level of the blister • for immunohistochemistry, it will be frozen or can be put in Michel media  for immunohistochemistry, it will be frozen or can be put in Michel media if an autoimmune blistering disease (AIBD) is suspected, the biopsy will be o if an autoimmune blistering disease (AIBD) is suspected, the biopsy will be # performed on healthy perilesional skin and processed for direct immunofluo- performed on healthy perilesional skin and processed for direct immunofluo‐ rescence (DIF) rescence (DIF) if a genodermatosis is suspected, the biopsy will also be taken between the o if a genodermatosis is suspected, the biopsy will also be taken between the nor‐ # normal skin and the edge of the blister and processed for immunomapping mal skin and the edge of the blister and processed for immunomapping with with specialized antibodies (DIF or immunoperoxidase) specialized antibodies (DIF or immunoperoxidase)

FigureFigure 1. 1.Skin Skin biopsy biopsy for for EBH, EBH, between between normal normal skin skin and and the the edge edge of of the the blister. blister.

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2. Etiologies 2.1. Infections Infections are the first cause of blistering eruption in neonates and infants.

2.1.1. Staphylococcal Scalded Skin Syndrome (SSSS) SSSS is an exfoliative, toxin‐mediated eruption caused by certain strains of Staphylo‐ coccus aureus producing an epidermolytic toxin (formerly named exfoliatin). The disease affects mostly neonates and children under 5 years of age but can also affect adults. In Dermatopathology 2021, 8 161 neonates, omphalitis is often the origin of the infection [2]. SSSS usually presents with prodromes (irritability, malaise, and fever) followed by a painful erythema, blistering with large areas of epidermal detachment, beginning on the face,2. Etiologies neck, axillae, and groin. SSSS is associated with a positive Nikolsky sign (Figure 2a). Mucosae2.1. Infections are not affected. TheInfections toxin in are SSSS the (and ﬁrst causealso bullous of blistering impetigo) eruption causes in a neonates cleavage and in the infants. granular layer. Skin biopsy is not always performed except in case of toxic epidermal necrosis (TEN) suspicion.2.1.1. Staphylococcal Scalded Skin Syndrome (SSSS) SSSS is an exfoliative, toxin-mediated eruption caused by certain strains of Staphylo- 2.1.2.coccus Histology aureus producing an epidermolytic toxin (formerly named exfoliatin). The disease affectsA subcorneal mostly neonates blister andis observed children along under the 5 granular years of agelayer but and can accompanied also affect adults.by a mild In inflammatoryneonates, omphalitis infiltrate is in often the epidermis the origin ofor thedermis. infection Acantholysis [2]. is often present, as shown in FigureSSSS 2b, usually and except presents in the with situation prodromes of an (irritability, old blister, malaise, no necrosis and is fever) observed. followed Dermal by a edemapainful and erythema, blood vessel blistering dilatation with largecan be areas observed of epidermal in the superficial detachment, dermis. beginning on the face,In neck, TEN, axillae, the blister and is groin. subepidermal SSSS is associated and epidermal with a necrosis positive is Nikolsky present; signa frozen (Figure section2a). canMucosae be performed are not affected. for quick results [3].

(a) (b)

FigureFigure 2. SSSS. 2. SSSS. (a) Clinical (a) Clinical appearance appearance of SSSSof SSSS with with Nikolsky Nikolsky sign. sign. (b ()b Hematein) Hematein eosin eosin× ×40:40: subcorneal subcorneal blister blister with with acantholysis. acantholysis.

2.1.3. TheImpetigo toxin in SSSS (and also bullous impetigo) causes a cleavage in the granular layer. BullousSkin biopsy impetigo is not usually always affects performed children except between in case 2 and of 5 toxic years epidermal of age but necrosis can be observed(TEN) suspicion. in infants. The disease is usually transmitted through direct contact and cutane‐ ous trauma is often found. Bullous impetigo is considered as a localized form of SSSS and 2.1.2. Histology caused by the same strains of S. aureus producing an epidermolytic toxin. Superficial ves‐ icles progressA subcorneal to a blisterflaccid is blister observed replaced along with the granular yellow crusting layer and after accompanied rupture with by a a mild pe‐ ripheralinflammatory peeling, infiltrate which in is thehelpful epidermis for the or diagnosis dermis. Acantholysis (Figure 3a). Bullous is often present,impetigo as is shown often locatedin Figure in2 infantsb, and exceptin moist in areas, the situation such as ofthe an perineum, old blister, axillae, no necrosis and neck is observed. folds, sparing Dermal the edema and blood vessel dilatation can be observed in the superficial dermis. mucosae [4]. In TEN, the blister is subepidermal and epidermal necrosis is present; a frozen section can be performed for quick results [3].

2.1.3. Impetigo Bullous impetigo usually affects children between 2 and 5 years of age but can be observed in infants. The disease is usually transmitted through direct contact and cutaneous trauma is often found. Bullous impetigo is considered as a localized form of SSSS and caused by the same strains of S. aureus producing an epidermolytic toxin. Superﬁcial vesicles progress to a ﬂaccid blister replaced with yellow crusting after rupture with a peripheral peeling, which is helpful for the diagnosis (Figure3a). Bullous impetigo is often located in infants in moist areas, such as the perineum, axillae, and neck folds, sparing the mucosae [4]. Dermatopathology 2021, 8, 4

2.1.4. Histology Skin biopsy is rarely necessary. As in SSSS, the cleavage is subcorneal and the blister usu‐ ally contains neutrophils (Figure 3b), acantholytic cells, and sometimes Gram‐positive germs. Dermatopathology 2021, 8 Superficial dermis is inflammatory (lymphocytes and neutrophils). 162 The main differential diagnosis of impetigo is superficial pemphigus in cases with acantholytic cells [5].

(a) (b)

FigureFigure 3. Impetigo.3. Impetigo. (a )(a Post-bullous) Post‐bullous lesion lesion of of impetigo. impetigo. ((b) PAS staining ×× 20:20: Impetigo, Impetigo, vesicles vesicles filled ﬁlled with with neutrophils. neutrophils.

2.1.4.2.1.5. Histology Scabies SkinScabies biopsy is a iscontagious rarely necessary. disorder Ascaused in SSSS, by the the infestation cleavage is of subcorneal the skin with and Sarcoptes the blister usuallyscabiei var. contains hominis neutrophils. It can occasionally (Figure3b), have acantholytic a blistering cells, presentation, and sometimes as in Figure Gram-positive 4a. germs.In infants, palms and soles are often involved as well as the sides of the feet. SuperficialThe presence dermis of an isindividual inflammatory or familial (lymphocytes pruritus, often and neutrophils). during night, provides clin‐ ical Theorientation main differential [5]. diagnosis of impetigo is superficial pemphigus in cases with acantholytic cells [5]. 2.1.6. Histology 2.1.5.A Scabies skin biopsy is not performed to confirm the diagnosis of scabies but usually be‐ Dermatopathology 2021, 8, cause of the suspicion of another diagnosis, such as an autoimmune blistering disease. 5 Scabies is a contagious disorder caused by the infestation of the skin with Sarcoptes scabieiThevar. epidermishominis. It is can acanthotic occasionally with an have important a blistering spongiosis presentation, resulting as in Figurevesiculation4a. and blistering (Figure 4b), with exocytosis of eosinophils and neutrophils. Serial cuts can reveal the female mite and her eggs in the stratum corneum. An important inflammatory cell infiltrate is present in the dermis, along the vessels and adnexae, made of lympho‐ cytes, histiocytes, and eosinophils. Langerhans cells may be numerous and sometimes , if an immunohistochemistry with anti‐CD1a antibody is performedit can be misleading and result in a Langerhans cell histiocytosis diagnosis. Flame figures are often present in in‐ fants.

(a) (b)

FigureFigure 4. Scabies.4. Scabies. (a )(a Blistering) Blistering scabies. scabies. ( b(b)) Hematein Hematein eosineosin ××20:20: dermo dermo-epidermal‐epidermal blister blister and and inflammatory inﬂammatory infiltrate inﬁltrate with with eosinophilseosinophils in in the the dermis. dermis.

2.2. Genodermatosis 2.2.1. Hereditary Epidermolysis Bullosa Inherited epidermolysis bullosa (EB) comprises a highly heterogeneous group of rare diseases characterized by fragility and/or blistering of the skin and mucosae. EB type and subtype classification is presently defined by “onion skin”, terminology based on the com‐ bination of level of skin cleavage corresponding to the major EB type, the clinical severity, the inheritance pattern, and the molecular defect, including the relative protein expression and the disease‐causing sequence variant. (Table 2) [6]. There are four main subtypes: EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler syndrome [7]. In these four subtypes, mucocutaneous fragility is the result of abnormalities of the cutaneous basement membrane zone (BMZ) (hemidesmosomes, focal adhesions, anchor‐ ing filaments, and anchoring fibrils) [8]. The clinical appearance depends on the level of skin cleavage: superficial blisters or erosions will occur with EBS, and blisters will be more profound with JEB, DEB, and KS, and lead to ulcerations. Blisters may be generalized or localized to the extremities, as shown in Figure 5a,b. The skin defects heal with dyschromia, atrophy, and scarring. Mucosae and skin ad‐ nexa (nails, hair) are also affected. A correct and rapid diagnosis of EB type is mandatory for an optimal management of the baby, for parent information about prognosis, for therapeutic options, and also for genetic counseling. Immunomapping is the first diagnostic step as it can deliver rapid results in less than 48 h [8].

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In infants, palms and soles are often involved as well as the sides of the feet. The presence of an individual or familial pruritus, often during night, provides clinical orientation [5].

2.1.6. Histology A skin biopsy is not performed to confirm the diagnosis of scabies but usually because of the suspicion of another diagnosis, such as an autoimmune blistering disease. The epidermis is acanthotic with an important spongiosis resulting in vesiculation and blistering (Figure4b), with exocytosis of eosinophils and neutrophils. Serial cuts can reveal the female mite and her eggs in the stratum corneum. An important inflammatory cell infiltrate is present in the dermis, along the vessels and adnexae, made of lymphocytes, histiocytes, and eosinophils. Langerhans cells may be numerous and sometimes, if an immunohistochemistry with anti-CD1a antibody is performedit can be misleading and result in a Langerhans cell histiocytosis diagnosis. Flame figures are often present in infants.

Table 2. Classical types of EB (adapted from Ref. [6]).

Level of Skin Cleavage EB Type Inheritance Mutated Gene (s) Targeted Protein (s) Autosomal Intraepidermal EB simplex KRT5, KRT14 Keratin 5, keratin 14 dominant PLEC Plectin KLHL24 Kelch-like member 24 Autosomal KRT5, KRT14 Keratin 5, keratin 14 recessive Bullous pemphigoid antigen 230 (BP230) DST (syn. BPAG1e, dystonin) Exophilin-5 (syn. synaptotagmin-like EXPH5 (syn. SLAC2B) protein homolog lacking C2 domains b, Slac2-b) PLEC Plectin CD151(syn. TSPAN24) CD151 antigen (syn. tetraspanin 24) Junctional Autosomal LAMA3, LAMB3, Junctional Laminin 332 EB recessive LAMC2 COL17A1 Type XVII collagen ITGA6, ITGB4 Integrin a6b4 ITGA3 Integrin a3 subunit Dystrophic Autosomal Dermal COL7A1 Type VII collagen EB dominant Autosomal COL7A1 Type VII collagen recessive Autosomal Fermitin family homolog 1 (syn. Mixed Kindler EB FERMT1 (syn. KIND1) recessive kindlin-1)

There are four main subtypes: EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler syndrome [7]. Dermatopathology 2021, 8 164

In these four subtypes, mucocutaneous fragility is the result of abnormalities of the cutaneous basement membrane zone (BMZ) (hemidesmosomes, focal adhesions, anchoring filaments, and anchoring fibrils) [8]. The clinical appearance depends on the level of skin cleavage: superficial blisters or erosions will occur with EBS, and blisters will be more profound with JEB, DEB, and Dermatopathology 2021, 8, 7 KS, and lead to ulcerations. Blisters may be generalized or localized to the extremities, as shown in Figure5a,b.

(a) (b)

(e)

Figure 5. Cont. Dermatopathology 2021, 8 165 Dermatopathology 2021, 8, 8

(f1) (f2)

(f3) (f4)

(g1) (g2)

Figure 5. Cont. Dermatopathology 2021, 8 166 Dermatopathology 2021, 8, 9

(g3) (g4)

(g5)

FigureFigure 5.5. HereditaryHereditary epidermolysisepidermolysis bullosa.bullosa. ((aa)) GeneralisedGeneralised blistersblisters inin EBS.EBS. ((bb)) CutaneousCutaneous aplasiaaplasia in in EBJ. EBJ. ( (cc)) EBS: EBS: intraepi- intraep‐ idermal cleavage. (d) EBJ: cleavage in lamina lucida. (e) EBD: cleavage in anchoring fibrils. (f) EB simplex: (f1) Hematein dermal cleavage. (d) EBJ: cleavage in lamina lucida. (e) EBD: cleavage in anchoring fibrils. EB simplex: (f1) Hematein eosin eosin ×10: blister at the DEJ with vacuolization of basal keratinocytes (arrows) and remnants of basal keratinocytes (aster‐ ×10: blister at the DEJ with vacuolization of basal keratinocytes (arrows) and remnants of basal keratinocytes (asterisk) on isk) on the floor of the blister; (f2) immunohistochemistry with anti‐pan cytokeratin antibody showing positivity on the theroof floor and ofthe the floor blister; of the (f2 blister;) immunohistochemistry (f3,f4) immunohistochemistry with anti-pan with cytokeratin anti‐laminin antibody and anti showing‐collagen positivity VII antibodies on the roofshowing and thepositivity floor of on the the blister; floor (off3 the,f4) blister. immunohistochemistry (g) Dystrophic EB: with (g1 anti-laminin) Hematein eosin and anti-collagen X10 blister at VII the antibodies DEJ; (g2) immunohistochem showing positivity‐ onistry the with floor anti of‐ thepan blister. cytokeratin Dystrophic antibody EB: showing (g1) Hematein positivity eosin on X10 the blisterroof of at the the blister; DEJ; ((g2g3)) immunohistochemistry immunohistochemistry withwith anti-pananti‐laminin cytokeratin showing antibody positivity showing on the roof positivity of the onblister; the roof and of(g4 the) anti blister;‐collagen (g3) immunohistochemistryVII antibodies showing absence with anti-laminin of expres‐ showingsion compared positivity to a on control the roof (g5 of). the blister; and (g4) anti-collagen VII antibodies showing absence of expression compared to a control (g5). The skin defects heal with dyschromia, atrophy, and scarring. Mucosae and skin adnexa (nails, hair) are also affected. A correct and rapid diagnosis of EB type is mandatory for an optimal management of the baby, for parent information about prognosis, for therapeutic options, and also for genetic counseling. Immunomapping is the first diagnostic step as it can deliver rapid results in less than 48 h [8]. Dermatopathology 2021, 8 167

2.2.2. Histology The biopsy (see technique above) must be taken in a fresh lesion because, after a short delay, re-epithelialization occurs, and the real level of the blister will be difficult to assess. Standard histology will usually show a subepidermal blister in all subtypes; the epidermis is usually intact, except in an old biopsy in which necrosis of the epidermis can be observed. In EBS, eosinophilic granules corresponding to tonofilaments clumping may be present, as well as modifications of basal keratinocytes (vacuolisation) and occasionally keratinocyte remnants are present on the floor (Figure5(f1)). The blister is usually empty without inflammatory cells when recent, but inflammation can occasionally be observed. The floor of the blister is made of dermis with conservation of the papillary relief and no or little inflammation, except in the case of generalized EBS. Dermatopathology 2021, 8, 10 Immunomapping will be performed on the fixed and frozen biopsies to assess the level of cleavage of the blister (Figure6).

FigureFigure 6. Decision6. Decision tree. tree.

2.2.3.The Keratinopathic location of the Ichthyosis cleavage is (KI) detailed in Figure5c–e. InKI general is a new pathology umbrella laboratories, term defined immunohistochemistry by the First Ichthyosis with Consensus anti-pan Conference cytokeratin in andSorèze anti-collagen in 2009, which 4 antibodies revised canthe nomenclature be used to provide and classification rapid results. of inherited ichthyoses [9]. InKI specialized encompasses centers, ichthyoses three maincaused antibodies by keratin can mutations, be introduced namely as epidermolytic a ﬁrst step for ich‐ immunomappingthyosis (EI), superficial because epidermolytic they are necessary ichthyosis for diagnosis (SEI), and of other the three non main‐blistering EB subtypes variants. (EBS, JEB,Newborns DEB): may show widespread blistering resembling epidermolysis bullosa (Fig‐ - ureanti-pan 7a), or have cytokeratin severe erythroderma AE1/AE3 requiring a specific management, so an early diag‐ - nosisanti-laminin is therefore antibody necessary. - anti-collagenA correct diagnosis VII antibody of ichthyosis is essential for genetic counseling but also for pa‐ tientIf necessary,information other about specialized prognosis antibodies and therapeutic are introduced options. to study the other proteins of the DEJThese (anti-integrin, rare keratinization anti-plectin, disorders anti-BP180). are due to pathogenic variants in the genes en‐ codingFigure keratins5(f1–g5) 1, show2, or 10. examples Mutations of immunomapping result in keratin clumping in two different and collapse subtypes of ofthe EB. cyto‐ skeleton in the suprabasal keratinocytes (keratin 1 or 10) or upper layers (keratin 2). The presence of palmoplantar keratoderma (Figure 7b) provides clinical orientation for keratin 1 mutations as keratin 10 is absent in palms and soles.

2.2.4. Histology The histological diagnosis of EI will easily and quickly help the physician, since the appearance of epidermolysis is visible at a low magnification with the typical appearance of epidermolytic hyperkeratosis [10–12], with vacuolated suprabasal keratinocytes, affect‐ ing the upper part or the entire epidermis with or without a blister formation (Figure 7c). The stratum corneum can become very thick following the first days of life, sometimes compact or more basket‐weave like. The granular layer is also affected, containing baso‐ philic granules and the keratinocytes containing eosinophilic granules, corresponding to clumps of tonofilaments in electron microscopy (Figure 7d). Interestingly, the diagnosis of KI can be performed very early in life and the diagnosis can be very fast in a newborn just by the examination of a frozen section, therefore elimi‐ Dermatopathology 2021, 8 168

Dermatopathology 2021, 8, 2.2.3. Keratinopathic Ichthyosis (KI) 11

KI is a new umbrella term defined by the First Ichthyosis Consensus Conference in Sorèze in 2009, which revised the nomenclature and classification of inherited ichthyoses [9]. natingKI the encompasses other differential ichthyoses diagnosis caused of extensive by keratin skin mutations, blisters, such namely as infection epidermolytic or he‐ ichthyosisreditary epidermolysis (EI), superficial bullosa. epidermolytic In our experience, ichthyosis (SEI),the clinical and other appearance non-blistering does not variants. corre‐ late withNewborns the intensity may show of histologic widespread abnormalities. blistering resembling epidermolysis bullosa (Figure7a) , or haveRecently, severe Galler erythroderma et al. [13] requiringreported the a specific opportunity management, of a quick so diagnosis an early with diagnosis minimal is thereforetrauma to necessary. the patient by performing the “jelly‐roll” technique. The observation of the roof of a blisterA correct shows diagnosis characteristic of ichthyosis findings is essential of epidermolytic for genetic hyperkeratosis, counseling but which also for included patient informationhyperkeratosis about with prognosis granular and layer therapeutic degeneration, options. vacuolization, and eosinophilic glob‐ These rare keratinization disorders are due to pathogenic variants in the genes en- ules. The authors suggest that this technique can be used for the diagnosis of EI. coding keratins 1, 2, or 10. Mutations result in keratin clumping and collapse of the The histology of SEI shares the appearance of classical EI but is restricted to the more cytoskeleton in the suprabasal keratinocytes (keratin 1 or 10) or upper layers (keratin 2). superficial spinous and granular cell layers (Figure 7e) with possible intracorneal blister The presence of palmoplantar keratoderma (Figure7b) provides clinical orientation formation [14]. The distribution of granular degeneration is consistent with the expression for keratin 1 mutations as keratin 10 is absent in palms and soles. site of keratin 2.

(a) (b)

Figure 7. Cont. Dermatopathology 2021, 8 169

Dermatopathology 2021, 8, 12

(e)

FigureFigure 7.7.Epidermolytic Epidermolytic ichthyosis. ichthyosis. (a )(a Newborn) Newborn with with superficial superficial blisters blisters and and erythroderma. erythroderma. (b) Palmoplantar (b) Palmoplantar keratoderma kerato‐ indermaCK1 mutation.in CK1 mutation.(c) Hematein (c) Hematein eosin × 10:eosin confluent ×10: confluent epidermolysis epidermolysis leading leading to blister. to ( blister.d) Hematein (d) Hematein eosin × 20:eosin epidermolysis ×20: epider‐ withmolysis basophilic with basophilic and eosinophilic and eosinophilic granules. granules. (e) Hematein (e) Hematein eosin ×20: eosin SEI, epidermolysis×20: SEI, epidermolysis is located is in located the granular in the layer. granular layer. 2.2.4. Histology 2.2.5. Incontinentia Pigmenti (IP) The histological diagnosis of EI will easily and quickly help the physician, since the IP is a rare X‐linked dominant genodermatosis caused by mutations in the inhibitor appearance of epidermolysis is visible at a low magnification with the typical appearance of of the kappa B kinase gamma (IKBKG) (previously known as NEMO or nuclear factor epidermolytic hyperkeratosis [10–12], with vacuolated suprabasal keratinocytes, affecting kappa B essential modulator) gene. IP affects mostly female patients and is usually lethal the upper part or the entire epidermis with or without a blister formation (Figure7c). The in utero for males, but cases in boys are reported [15,16]. The phenotype in females is stratum corneum can become very thick following the first days of life, sometimes compact variable, manifestations being dependent on the effects of mosaicism resulting from X‐ or more basket-weave like. The granular layer is also affected, containing basophilic chromosome lyonization. granules and the keratinocytes containing eosinophilic granules, corresponding to clumps of tonofilamentsIP is a multisystem in electron disorder microscopy of ectodermal (Figure7 origind). and skin lesions may be associated withInterestingly, dental, ocular, the and diagnosis neurologic of KI abnormalities. can be performed The very skin early is almost in life always and the involved diagnosis in canneonates. be very The fast lesions in a newborn are classically just by the vesiculobullous, examination of afollowing frozen section, the Blaschko therefore lines, eliminat- and ingrepresent the other the differential first stage of diagnosis cutaneous of extensive involvement. skin blisters,They are such usually as infection located oron hereditary the limbs, epidermolysistrunk, and scalp bullosa. (Figure In 8a). our Later experience, stages are the characterized clinical appearance by verrucous does not papules correlate (stage with 2), thewhorled intensity hyperpigmentation of histologic abnormalities. (stage 3), and pallor and scarring (stage 4); different stages may Recently,overlap and Galler only et stages al. [13 ]1, reported 2, and 3 thecan opportunity be seen in infants. of a quick Skin diagnosis histology with is helpful minimal for traumaall 4 stages to the [17]. patient by performing the “jelly-roll” technique. The observation of the roof of a blisterThe differential shows characteristic diagnosis of findings IP lesions of epidermolyticin newborns are hyperkeratosis, herpes simplex which infection, included con‐ hyperkeratosisgenital varicella, with and granular autoimmune layer degeneration,blistering diseases, vacuolization, but the Blaschko and eosinophilic‐linear disposition globules. Theof the authors lesion suggest is helpful. that thisGenodermatosis, technique can including be used for Conradi–Hunermann–Happle the diagnosis of EI. syn‐ dromeThe or histology Goltz syndrome, of SEI shares needs the to appearance be ruled out of with classical histology. EI but is restricted to the more superficialThe skin spinous biopsy and is therefore granular always cell layers performed (Figure7 ande) with of great possible help. intracorneal blister formation [14]. The distribution of granular degeneration is consistent with the expression site2.2.6. of Histology keratin 2. At stage 1, eosinophilic spongiosis is observed, and its confluence leads to vesicula‐ 2.2.5.tion and Incontinentia blisters (Figure Pigmenti 8b). Dyskeratotic/apoptotic (IP) keratinocytes (isolates or aggregates) are anIP important is a rare X-linked clue for dominant diagnosis genodermatosis and can be assessed caused with by serial mutations cuts when in the necessary inhibitor of(Figure the kappa 8c). An B inflammatory kinase gamma dermal (IKBKG) infiltrate (previously with eosinophils known as may NEMO be present. or nuclear Free factor mel‐ kappaanin can B essentialbe observed modulator) in the dermis gene. even IP affects at stage mostly 1. In cases female with patients an overlap and is between usually stages lethal 1 and 2, hyperkeratosis, papillomatosis, and acanthosis can be present, as well as numer‐ ous apoptotic cells. Dermatopathology 2021, 8 170

in utero for males, but cases in boys are reported [15,16]. The phenotype in females is variable, manifestations being dependent on the effects of mosaicism resulting from X-chromosome lyonization. IP is a multisystem disorder of ectodermal origin and skin lesions may be associated with dental, ocular, and neurologic abnormalities. The skin is almost always involved in neonates. The lesions are classically vesiculobullous, following the Blaschko lines, and represent the ﬁrst stage of cutaneous involvement. They are usually located on the limbs, trunk, and scalp (Figure8a). Later stages are characterized by verrucous papules (stage 2), whorled hyperpigmentation (stage 3), and pallor and scarring (stage 4); different stages may overlap and only stages 1, 2, and 3 can be seen in infants. Skin histology is helpful for Dermatopathology 2021, 8, 13 all 4 stages [17].

(a) (b)

(c) Figure 8. Incontinentia pigmenti. (a) Newborn with blistering Blaschko‐linear eruption. (b) Hematein eosin ×40: spongiosis Figure 8. Incontinentia pigmenti. (a) Newborn with blistering Blaschko-linear eruption. (b) Hematein eosin ×40: spongiosis with eosinophils leading to vesicles. (c) Hematein eosin ×20: numerous apoptotic keratinocytes. with eosinophils leading to vesicles. (c) Hematein eosin ×20: numerous apoptotic keratinocytes. 2.3. Cell Proliferation 2.3.1.The Mastocytosis differential diagnosis of IP lesions in newborns are herpes simplex infection, congenital varicella,Mastocytosis and is autoimmune caused by a clonal blistering mast cell diseases, proliferation but theassociated Blaschko-linear with somatic disposition ac‐ of tivating mutations in c‐kit. All forms of cutaneous mastocytosis may be associated with blistering in infancy, but the most frequent form associated with blisters is solitary mas‐ tocytoma. Clinical assessment will find a history of infiltrated red/purple lesions associ‐ ated with the occurrence of blisters. Another very rare presentation is diffuse cutaneous mastocytosis (DCM) in a neonate having erythroderma and generalized blisters, and may Dermatopathology 2021, 8 171

the lesion is helpful. Genodermatosis, including Conradi–Hunermann–Happle syndrome or Goltz syndrome, needs to be ruled out with histology. The skin biopsy is therefore always performed and of great help.

2.2.6. Histology At stage 1, eosinophilic spongiosis is observed, and its confluence leads to vesiculation and blisters (Figure8b). Dyskeratotic/apoptotic keratinocytes (isolates or aggregates) are an important clue for diagnosis and can be assessed with serial cuts when necessary (Figure8c). An inflammatory dermal infiltrate with eosinophils may be present. Free melanin can be observed in the dermis even at stage 1. In cases with an overlap between stages 1 and 2, hyperkeratosis, papillomatosis, and acanthosis can be present, as well as numerous apoptotic cells.

2.3. Cell Proliferation 2.3.1. Mastocytosis Mastocytosis is caused by a clonal mast cell proliferation associated with somatic Dermatopathology 2021, 8, activating mutations in c-kit. All forms of cutaneous mastocytosis14 may be associated with

blistering in infancy, but the most frequent form associated with blisters is solitary masto- cytoma. Clinical assessment will ﬁnd a history of inﬁltrated red/purple lesions associated be so serious that it mimics staphylococcal scalded skin syndrome (Figure 9a). The epi‐ sodeswith of skin the blisters occurrence are accompanied of blisters. by pruritus Another and veryredness rare all over presentation the body. The is diffuse cutaneous masto- tendencycytosis to blister (DCM) usually in aimproves neonate over having 3–4 years erythroderma [18–20]. and generalized blisters, and may be so serious that it mimics staphylococcal scalded skin syndrome (Figure9a). The episodes of 2.3.2. Histology skinSkin blisters biopsy shows are a accompanied subepidermal blister by surrounding pruritus a and dense redness dermal mast all cell over in‐ the body. The tendency to filtrateblister (Figure usually 9b). Immunohistochemistry improves over is 3–4 positive years for [the18 –c‐20kit ].(anti‐CD117) antibody (Figure 9c).

(a) (b)

(c) Figure 9. Mastocytosis. (a) Generalized blisters. (b) Hematein eosin ×40: floor of the blister, conser‐ vationFigure of papillary 9. Mastocytosis. relief, and dense mastocytes (a) Generalized infiltrate. (c) Immunohistochemistry blisters. (b) Hematein with anti‐ eosin ×40: floor of the blister, CD117conservation antibody ×10: positivity of papillary of the dermal relief, infiltrate. and dense mastocytes infiltrate. (c) Immunohistochemistry with 2.3.3.anti-CD117 Langerhans antibody Cell Histiocytosis×10: positivity(LCH) of the dermal infiltrate. LCH is a rare disease characterized by the aberrant clonal proliferation of Langerhans cells. Blistering presentation in cutaneous Langerhans cell histiocytosis, even if infrequent, may happen in the self‐healing form (Figure 10a) [21–24].

Dermatopathology 2021, 8 172

Dermatopathology 2021, 8, 15

2.3.2. Histology Skin biopsy shows a subepidermal blister surrounding a dense dermal mast cell 2.3.4.inﬁltrate Histology (Figure 9b). Immunohistochemistry is positive for the c-kit (anti-CD117) antibody(Langerhans Figure9c). cells (LC) have coffee‐bean or kidney‐shaped nuclei. The histiocytic in‐ filtrate2.3.3. Langerhans is epidermotropic Cell Histiocytosis and also situated (LCH) in the papillary dermis, sometimes extending to the reticular dermis. The blister is situated at the dermo‐epidermal junction. In the der‐ LCH is a rare disease characterized by the aberrant clonal proliferation of Langerhans mis, the infiltration is often associated with eosinophils and lymphocytes (Figure 10b). cells. Blistering presentation in cutaneous Langerhans cell histiocytosis, even if infrequent, Detection of LC markers (CD1a and CD207 on formalin‐fixed sample) is mandatory may happen in the self-healing form (Figure 10a) [21–24]. to confirm the diagnosis (Figure 10c).

(a) (b)

(c)

Figure 10. LangerhansLangerhans cell cell histiocytosis. histiocytosis. (a) ( aBlister) Blister in ina neonate. a neonate. (b) Hematein (b) Hematein eosin eosin ×40: ×papillary40: papillary infiltration infiltration with Lang with‐ Langerhanserhans cell, exocytosis cell, exocytosis resulting resulting in blister in blister and crusts, and crusts, eosinophilic eosinophilic infiltrate infiltrate in the in dermis. the dermis. (c) Immunohistochemistry (c) Immunohistochemistry with anti‐CD1a antibody ×5: positivity of the dermal infiltrate. with anti-CD1a antibody ×5: positivity of the dermal infiltrate. 2.3.5. Auto‐Immune Blistering Diseases 2.3.4. Histology BullousLangerhans Pemphigoid cells (BP) (LC) have coffee-bean or kidney-shaped nuclei. The histiocytic infiltrate is epidermotropic and also situated in the papillary dermis, sometimes extending Bullous pemphigoid (BP), usually seen in elderly populations, is a rare condition in to the reticular dermis. The blister is situated at the dermo-epidermal junction. In the children. Like in adults, tense serous fluid‐filled or hemorrhagic bullae occur on an in‐ dermis, the infiltration is often associated with eosinophils and lymphocytes (Figure 10b). flammatory base or urticated plaques. The eruption is widespread and mucous mem‐ branes are not affected. Acral involvement (palms, soles, and head) is more common in infantile BP, sometimes with a bunch of grapes appearance (Figure 11) [25–27]. Dermatopathology 2021, 8 173

Detection of LC markers (CD1a and CD207 on formalin-ﬁxed sample) is mandatory to conﬁrm the diagnosis (Figure 10c).

2.3.5. Auto-Immune Blistering Diseases Bullous Pemphigoid (BP) Bullous pemphigoid (BP), usually seen in elderly populations, is a rare condition in children. Like in adults, tense serous fluid-filled or hemorrhagic bullae occur on an inflammatory base or urticated plaques. The eruption is widespread and mucous membranes are Dermatopathology 2021, 8, not affected. Acral involvement (palms, soles, and head) is more common in infantile BP,16 sometimes with a bunch of grapes appearance (Figure 11)[25–27].

Figure 11. Bullous pemphigoid with typical appearance of bunch of grapes on the hand of an in‐ Figure 11. Bullous pemphigoid with typical appearance of bunch of grapes on the hand of an infant. fant. 2.3.6. Histology 2.3.6.Skin Histology histology is not different from BP in adults: subepidermal blistering is observed associatedSkin withhistology an inflammatory is not different infiltrate from BP made in adults: of eosinophils subepidermal and often blistering neutrophils. is observed associatedHistopathology with an inflammatory shows eosinophilic infiltrate spongiosis made of with eosinophils clefting. and DIF often reveals neutrophils. linear deposition ofHistopathology IgG and/or C3 shows along eosinophilic the basement spongiosis membrane. with IgA clefting. deposition DIF isreveals also often linear seen. dep‐ osition of IgG and/or C3 along the basement membrane. IgA deposition is also often seen. 2.3.7. Other AIBDs 2.3.7.The Other other AIBDs AIBDs are less frequent in this age group, since only about 50 cases of neonatalThe AIBDs other wereAIBDs identified are less frequent in a systematic in this reviewage group, of the since literature only about [28]. 50 cases of ne‐ onatalPemphigus AIBDs were vulgaris, identified pemphigus in a systematic foliaceus, review bullous of the pemphigoid, literature [28]. pemphigoid ges- tationis,Pemphigus IgA-linear vulgaris, dermatosis, pemphigus and epidermolysis foliaceus, bullous bullosa pemphigoid, acquisita have pemphigoid been reported gesta‐ intionis, babies IgA of‐linear affected dermatosis, mothers (antibodies and epidermolysis are passively bullosa transferred acquisita have from been the motherreported to in thebabies neonate). of affected Pemphigoid mothers diseases (antibodies are more are passively likely to presenttransferred after from birth the and mother were more to the predominantneonate). Pemphigoid in males [25 diseases–27]. are more likely to present after birth and were more pre‐ dominantSkin histology in males does [25–27]. not differ from adult AIBDs. Skin histology does not differ from adult AIBDs. 2.3.8. Drug Reactions 2.3.8.Exposure Drug Reactions to different medications can occur for the first time during infancy. Adverse drug reactions can have a blistering presentation, mostly in erythema multiforme (EM), Exposure to different medications can occur for the first time during infancy. Adverse Stevens–Johnson syndrome (SJS), and toxic epidermal necrolysis. drug reactions can have a blistering presentation, mostly in erythema multiforme (EM), Stevens–Johnson syndrome (SJS), and toxic epidermal necrolysis. In children, EM and SJS cases are often due to infections of herpes simplex virus (HSV) or Mycoplasma, while TEN is often associated with drugs [4]. As discussed above, TEN and SSSS can have a close clinical presentation and skin biopsy is useful to differentiate SSSS and TEN. However, skin histology does not differ from adults for EM, SJS, and TEN.

In children, EM and SJS cases are often due to infections of herpes simplex virus (HSV) or Mycoplasma, while TEN is often associated with drugs [4]. As discussed above, TEN and SSSS can have a close clinical presentation and skin biopsy is useful to differentiate SSSS and TEN. However, skin histology does not differ from adults for EM, SJS, and TEN.

3. Conclusions The onset of blisters in a neonate or an infant is most often a diagnostic challenge for physicians, and the underlying cause has to be determined quickly between several etiologies. The clinical context must be discussed with the clinician as well as the best technique for the biopsy. Skin biopsy, often necessary, is particularly helpful for a rapid and precise diagnosis, leading to an appropriate management of the baby.

Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Conﬂicts of Interest: The author declares no conﬂict of interest.

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