10 Differential Diagnosis of Atopic Eczema

Chapter 10 10 Differential Diagnosis of Atopic Eczema B. Wedi, A. Kapp 10.1 Table 10.1. Differential diagnosis of atopic eczema Introduction Chronic inflammatory skin diseases Contact (allergic, irritant) Several studies demonstrate our difficulties in estab- Seborrhoeic dermatitis lishingthediagnosisofatopiceczema(AE).Itsun- Psoriasis Lichen simplex chronicus known aetiology, the wide range in symptomatology, and the fluctuating course, including the many eliciting Infectious agents Candida factors, form the background for these difficulties [1]. Dermatophytes During the past few decades, several proposals have Herpes simplex been made to establish diagnostic criteria for AE Staphylococcus aureus [2–5]. The main problem of most criteria is that they Sarcoptes scabiei HIV-associated dermatitis are not applicable to both adults and children and do Immunologic disorders not discriminate between the allergic IgE-mediated Dermatitis herpetiformis and the nonallergic type of AE [6, 7]. Pemphigus foliaceus The differential diagnosis of AE is closely related to Graft-versus-host disease theageofthepatient.Itincludesotherformsofecze- Dermatomyositis ma, immunodeficiencies associated with eczematoid Malignant Diseases rashes,infectiousdiseasesand infestations, metabolic Cutaneous T-cell lymphoma (mycosis fungoides, S´ezary syndrome) diseases, neoplastic diseases and other chronic inflam- Histiocytosis X (Letterer-Siwe disease) matory skin conditions (Table 10.1). Congenital disorders Netherton’s syndrome Dubowitz syndrome 10.2 Erythrokeratodermia variabilis Chronic Inflammatory Skin Diseases Immunodeficiencies Wiskott-Aldrich syndrome (immunodeficiency with thrombocytopenia and eczema) “Eczema” is a nonspecific term often confounding the Thymic hypoplasia (DiGeorge syndrome) clinical and histopathologic description of various Hyper-IgE syndrome unrelated inflammatory diseases. All eczemas are his- Severe combined immunodeficiency (SCID) tologically spongiotic, but not all spongiotic dermato- Ataxia teleangiectasia ses are clinically eczematous. The histology is mainly Metabolic Diseases noncontributive to the diagnosis, as there are no defi- Phenylketonuria Tyrosinemia nite features allowing us to distinguish between AE and Histidinemia other forms of eczema. The eczematous eruptions all Zinc deficiency manifest T-cell proinflammatory mediator involve- Pyridoxine (vitamin B6) and niacin deficiency ment, yet may be quite different clinically [8]. Multiple carboxylase deficiency Differentiating seborrhoeic dermatitis from AE may Nonallergic reaction to medication be difficult in an infant less than 6 months old. The dif- Infliximab 10.4 Immunologic Disorders 101 ferential diagnosis of AE and seborrheic dermatitis is such as sinusitis, asthma, and hyper-IgE syndrome, most often complicated by the seemingly definite seb- and laboratory abnormalities such as elevated IgE lev- orrheic dermatitis developing into the later condition. els, eosinophilia, and possible TH1-TH2 imbalances, Seborrheic dermatitis is characterized by onset during suggestapredilectionforatopicdisordersinthese the 1st days or weeks of life, absence of pruritus, and patients. presence of greasy scaling on a yellow-red base. Involvement of the top of the scalp (cradle cap), axilla, and diaper area makes it more likely the patient has 10.4 seborrheic dermatitis, whereas excoriated dermatitis Immunologic Disorders involving the extensor surfaces, face, and trunk favour AE. Dermatitis herpetiformis Duhring (DHD) is an IgA- In patients with well-established AE who become mediated blistering skin disease characterized by the resistant to therapy, the possibility of contact dermati- presence of granular deposits of IgA in papillary der- tis to the topical therapy, including allergy to cortico- mis. The skin rash may resemble AE lesions and is glu- steroid or a preservative, should be considered [9, 10]. ten-dependent. Less than 10% of patients with DHD Inthesepatientspatchtestingshouldexcludeallergic have gastrointestinal symptoms suggestive of coeliac contact dermatitis, particularly in the case of localized disease, yet they all have gluten-sensitive enteropathy lesions.Interestingly,inanAustraliancontactdermati- [16]. tis clinic, approximately 20% of total cases consisted of Pemphigus foliaceus is an acquired superficial blis- AE without patch test positivity [11]. Three distribu- tering skin disease in which IgG autoantibodies target tion patterns predominated in this study: generalized the extracellular region of desmoglein 1, a member of dermatitis and dermatitis involving only the hands or the desmosomal cadherin family, responsible for adhe- face. sive function [17]. Due to superficial blistering, intact bullae are rarely found. Therefore, the skin lesions that are often distributed in seborrheic areas can mimic 10.3 acute/subacute eczema. Infection and Infestation The skin symptoms of graft-versus-host disease (GvHD) may resemble AE. Scabies may be misdiagnosed at any age with AE in Acute GvHD occurs during the first 100 days after presence of highly pruritic, erythematous papular transplantationinupto50%ofgraftrecipients,while lesions. In most cases, the typical burrows can be found chronic GvHD develops in about 30%–50%, usually on the flexor wrists, finger webs and genitalia. Similar within 100–500 days following allogeneic stem cell symptoms in other family members may point to the transplantation [18]. It can involve the skin, liver, gas- diagnosis scabies. Otherwise there is an enhanced sus- trointestinal tract, and less frequently the lungs, eyes ceptibilitytoinfectionwithSarcoptes scabiei in atopic and neuromuscular system. Initial symptoms of acute patients. GvHD may be pruritus and dysaesthesia or pain of the In addition, dermatophytosis and candidiasis as palms, soles and ears. Maculopapular exanthemas of well as infection with Herpes simplex and Staphylococ- the face, palms and soles are frequently seen. Acral and cus aureus maybeconfusedwithskinlesionsofAE. perifollicular papules and involvement are typical. In Complicating the differential diagnosis, patients suf- addition, xerostomia and nail manifestations can be fering from AE are predisposed to these infections and seen. infestations [10, 12, 13]. Initial symptoms of chronic GvHD may be a persis- Diseases of the skin are important signs of HIV tenterythemaofthefacewithpigmentation.Chronic infection in which dermatitis and eczema present GvHD may be limited or extensive, localized (about mostly as seborrheic dermatitis. In children with pae- 20%) or generalized (about 80%). Progressive chronic diatric AIDS, AE has been described in up to 50% of GvHD immediately follows acute GvHD (about 32%); cases[14].HIV-infectedadultscommonlydevelopa delayed chronic GvHD occurs after a disease-free inter- condition that strongly resembles AE and is some- val (about 36%) and de novo chronic GvHD occurs times called atopic-like dermatitis [15]. Conditions without prior acute GvHD [18]. 102 10 Differential Diagnosis of Atopic Eczema Localized chronic GvHD resembles lichen ruber ders including eczema. It can present clinically as planus, in about 3% a morphea or lichen sclerosus et patches, plaques, tumors or generalized erythroderma atrophicus. The generalized form is characterized by [21, 22]. Even though the prognosis is good in most scaly erythemas, telangiectasias and pigment anoma- patients with patch-stage disease, extracutaneous lies. Chronic disseminated GvHD may be lichenoid or spread involving any organ is possible and may eventu- sclerodermiform. Most cases show Wickham’s striae of ally lead to death. S´ezary syndrome is a systemic vari- the buccal mucosa. In about 40% of cases, the nails are ant and manifests as erythroderma with generalized involved. bright red, scaling skin and associated leukemia and The skin findings in dermatomyositis are character- lymphadenopathy. Multiple biopsies may be necessary istic,butinitiallytheymaybeconfusedwithatopic to confirm the diagnosis. Immunophenotyping and T- eczema. Dermatomyositis is an immune-mediated dis- cell receptor gene arrangement analysis confirming a ease of the muscle and the surrounding connective tis- malignant clone are sometimes helpful in diagnosis. sue which is more common in female patients. It is Moreover, in preexisting nonclassified chronic palmo- associated with an increased risk of cancer. plantar eczema that responds poorly to standard thera- The skin findings in dermatomyositis are character- pies, differential diagnosis of mycosis fungoides-type ized by a lilac discoloration of the eyelids (heliotrope cutaneous T cell lymphoma of the hands and soles rash), often with periorbital edema, and erythematous should be considered [23]. papules over knuckles (Gottron sign), elbows, knees, and upper chest and back. These lesions are frequently Histiocytosis X (Letterer-Siwe Disease). Though prin- photosensitive. Dilated nail-fold capillary loops can be cipally a paediatric disease, Langerhans cell histiocyto- found at the base of the fingernails. Although proximal sis can affect any age group. It can be unifocal (skeletal) and symmetrical muscle weakness is typical, skin or multifocal (skeletal and/or visceral). Head and neck lesions may exist without inflammatory myopathy manifestation may mimic eczema and can thus be mis- (amyopathic dermatomyositis) [19]. Interestingly, in diagnosedasAE.Typicalskinsymptomsarecrusted children the heliotrope rash and Gottron papules clas- purpuric papules and a scaly seborrhoeic-like eruption sically associated

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