Altered Lamellar Body Secretion and Stratum Corneum

OBSERVATION Altered Lamellar Body Secretion and Stratum Corneum Membrane Structure in Netherton Syndrome Differentiation From Other Infantile Erythrodermas and Pathogenic Implications

Manige´ Fartasch, MD; Mary L. Williams, MD; Peter M. Elias, MD

Background: The infant with Netherton syndrome (NS) tum corneum layer was largely replaced by parakera- typically displays a generalized erythroderma covered by totic cells. A distinctive feature—premature secretion of fine, translucent scales, which can be difficult to distin- lamellar body contents—occurred only in NS. Further- guish clinically from erythrodermic psoriasis, nonbul- more, lamellar body–derived extracellular lamellae and lous congenital ichthyosiform erythroderma, or other in- stratum corneum lipid membranes were separated ex- fantile erythrodermas. Some infants with NS develop tensively by foci of electron-dense material. Finally, trans- progressive hypernatremic dehydration, failure to thrive, formation of lamellar body–derived lamellae into ma- and enteropathy. Such complications can be fatal. Diag- ture lamellar membrane structures was disturbed in NS. nosis is typically delayed until the appearance of a pa- thognomonic hair shaft anomaly, trichorrhexis invagi- Conclusions: Premature lamellar body secretion and foci nata (bamboo hair). To facilitate the early diagnosis of of electron-dense material in the intercellular spaces of NS, we obtained biopsy specimens from 7 patients with stratum corneum, features not observed in other eryth- erythrodermic NS and compared their morphologic find- rodermic disorders, appear to be frequent and relatively ings to those of 3 patients with erythrodermic psoriasis specific markers for NS. These ultrastructural features and 2 with congenital ichthyosiform erythroderma. Bi- could permit the early diagnosis of NS before the appear- opsy specimens were processed for light and electron mi- ance of the hair shaft abnormality. These abnormalities croscopy using postfixation with osmium tetroxide and could explain the impaired permeability barrier in NS, ruthenium tetroxide. and account for hypernatremia and dehydration in infants with NS. Observation: In NS, and often in congenital ichthyosiform erythroderma and erythrodermic psoriasis, the stra- Arch Dermatol. 1999;135:823-832

ETHERTON syndrome ease.5,6 Although ILC is the predominant (NS) is a rare autosomal cutaneous manifestation in older pa- recessive disorder of tients with NS,5,7-10 erythrodermic infants cornification, character- with NS are often misdiagnosed as hav- ized by the triad of ich- ing the following: (1) another metabolic thyosis,N hair shaft defects, and atopy. The disease with generalized dermatitis, such nature of the ichthyosiform dermatosis in as immunodeficiency disorder with der- this syndrome has been the subject of con- matitis (so-called Leiner disease) or acro- siderable debate, raising the question of dermatitis enteropathica; (2) a severe form whether NS is a heterogeneous condi- of more common disorders, such as eryth- tion.1 Although some patients with NS re- rodermic psoriasis (PsoE)11; or (3) an- From the Department of veal a distinctive ichthyosiform pheno- other recessive disorder of cornification, Dermatology, University of type of erythematous, polycyclic plaques eg, nonbullous congenital ichthyosiform Erlangen/Nuremberg, Erlangen, with “double-edged” scale (ichthyosis lin- erythroderma (CIE).1,4,12,13 Because ILC and Germany (Dr Fartasch); the earis circumflexa [ILC]), this feature usu- its characteristic hair shaft abnormalities Departments of Dermatology ally appears after infancy,2 as do pili torti, typically do not become evident until after (Drs Williams and Elias) and trichorrhexis nodosa, and the pathogno- the first year of life, a definitive diagnosis Pediatrics (Dr Williams), monic trichorrhexis invaginata. Most in- of NS is usually delayed.6 University of California, San Francisco; and the Dermatology fants with NS display a generalized exfo- A high rate of morbidity and mortal- Service, Veterans liative erythroderma, with or without an ity accompanies the erythroderma in in- 3,4 5,6 Administration Medical Center, atopic diathesis. Recent studies suggest fants with NS. Although some au- San Francisco, Calif that ILC and erythroderma/dermatitis rep- thors5,14 suggest that systemic complications (Drs Williams and Elias). resent different phases of the same dis- of NS could be due to a severe, underlying

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 METHODS expression.23 Finally, for morphologic control studies, we used freshly excised, surgical margins from 9 subjects with- PATIENTS out skin disease (from extensor surface; upper arms).

In 6 of the 7 ultrastructurally studied NS cases, clinical data MORPHOLOGIC STUDIES were available. They showed generalized involvement with a congenital or early-onset ichthyosiform erythroderma After rinsing in buffer, biopsy specimens were fixed in (Table 1 and Figure 1). Table 1 summarizes the sex, age, cacodylate-buffered 2.5% glutaraldehyde and then divided, and clinical features of the patients at the time of investi- with one half postfixed with 0.5% ruthenium tetroxide gations. In all patients except patient 3, diagnosis was ul- and 0.25% aqueous potassium ferrocyanide,20,24 and the timately established by demonstration of the typical hair other in 1% aqueous osmium tetroxide containing potas- shaft defect. All patients showed marked inflammation with sium ferrocyanide in the dark at 4°C. Tissue sections were areas of oozing, and in some, superficial blisters and ero- dehydrated in graded ethanols and embedded in either sions. Elliptical or punch biopsy specimens were taken from ruthenium tetroxide–fixed samples (Spurr resin; Poly- involved, uninfected skin sites. sciences, Warrington, Pa) or osmium tetroxide–fixed Because of the close clinical resemblance of NS to PsoE samples (Epon 812; Polysciences). Thin sections were and CIE, we also analyzed biopsy specimens from in- examined before and after double staining with ethanolic volved skin from 3 patients with PsoE and 2 with CIE. Pa- uranyl acetate plus lead citrate on an electron microscope tients with CIE fulfilled the following published criteria for operated at 100 kV. Serial semithin sections of the osmium autosomal recessive ichthyosis21,22: collodion membrane at tetroxide–fixed samples were stained with 1% methylene birth followed by subsequent erythroderma and fine scales blue. Tissue specimens were also fixed and processed rou- in a generalized distribution and ectropion. Neither tinely for histologic testing, sectioned at 6 µm, and stained patient with CIE demonstrated genetic linkage to the trans- with hematoxylin-eosin, periodic acid-Schiff, and Giemsa glutaminase: 1 (TGase1) gene or abnormal TGase1 staining.

Table 1. Clinical Features of Erythrodermic Patients With Netherton Syndrome*

Noncutaneous Syndromes Patient No./ Biopsy Bamboo Hypernatremic Failure Sex/Age† Site Outcome Hair Phenotype Dehydration to Thrive Other 1/M/2 mo Buttock Death within 1 y + E + + Aminoaciduria, IgE 15, myocarditis, pneumonia, no diarrhea 2/F/18 mo Unknown Alive with disease + E 0 − Elevated IgE level 137 units (nlϽ15) at 1 mo with positive radioallergosorbent test result to milk (6825; nlϽ500); pneumonia in neonatal nursery; group A streptococcus septicemia at age 2 wks 4/M/4 y Buttock Alive with disease + E 0 + Diarrhea severe in infancy with low protein and albumin levels, IgE 4964 (1 y); IgE 500 (nlϽ25) at 2 y; recurrent pneumonia and skin infections; anaphylactic reactions to cinnamon and eggs 5/F/5 y Buttock Alive with disease + E 0 ++ Severe infantile diarrhea; developed hypoproteinemia and transient low zinc (normalized with replacement, did not recur); anaphylactic reactions to cinnamon, eggs, and brazil nuts; IgE 3250 at3y(nlϾ5.6) 6/M/1 y Buttock Alive with disease + E 0 + IgE 2000; new brother was also affected, especially on face, scalp, and diaper area 7/F/4 mo Back Alive with disease + E O ++ Severe failure to thrive without diarrhea; hypertonia; septicemia

*Plus signs indicate present; minus signs, absent; nl, normal; and double plus signs, severe. †There were no clinical data for patient 3. Patient 5 was the sister of patient 4.

immunodeficiency, recent studies6 demonstrate that, apart brane unit structures within the intercellular spaces of from markers of atopy such as increased IgE, significant the stratum corneum (SC). In this study, we attempted immune defects are not present. Others5,15-17 have pro- to delineate a structural basis for the putative permeabil- posed that increased rates of transcutaneous water loss, re- ity barrier abnormality in NS using ruthenium tetroxide sulting in hypernatremic dehydration and hypothermia in postfixation, which permits ultrastructural analysis of SC the neonatal period, are a more likely cause of morbidity membrane structures,18-20 and to compare these find- and mortality in NS. Such a pathogenic scenario implies ings with the ultrastructural characteristics of PsoE and that a severe disturbance in the cutaneous permeability bar- CIE—disorders that clinically resemble the erythroder- rier is an important feature of this subgroup of NS. mic form of NS. Our findings suggest first, that prema- The normal skin barrier is provided by hydropho- ture lamellar body (LB) secretion is a distinctive feature bic lipids organized into repeating arrays of lamellar mem- of erythrodermic NS, and second, that severe SC extra-

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 cellular abnormalities may account for the hyperna- tosis, accentuated rete ridges, and occasional long, nar- tremic dehydration seen in severely affected patients. row rete ridges (psoriasiform ichthyosis) (Table 2 and Figure 2, A).4 Marked parakeratosis—the absence or pres- RESULTS ence of only a partial granular layer—occurred commonly, whereas hypergranulosis was seen only focally in some pa- LIGHT MICROSCOPY tients. In 3 patients (2, 3, and 4), the SC was entirely parakeratotic. In all cases, the outermost nucleated cell lay- Netherton Syndrome ers did not flatten normally, instead showing irregularly distributed intracellular vacuolization and/or extracellu- Light microscopy of NS revealed psoriasiform features, with lar edema. Spongiosis was also pronounced in the lower varying degrees of epidermal acanthosis and hyperkera- epidermal cell layers. Focal accumulations of eosinophilic, periodic acid-Schiff–positive, diastase-resistant homogeneous material (Figure 2, B) occurred within the parakeratotic SC and focally within the stratum granulosum (SG) in only 1 patient (1).5,16,25-29 Finally, the papillary dermis showed a mild-to-marked perivascular inflammatory infiltrate consisting of histiocytes, lymphocytes, and some granulocytes, with regions of exocytosis.

Erythrodermic Psoriasis

Erythrodermic psoriasis was characterized by elongation of the epidermal rete ridges, with thickening of the deeper Figure 1. Clinical picture of patient 1 showing erythrodermic skin with extensions and papillary edema. Thinning of the suprapap- exfoliative appearance and pronounced scaling of the scalp and diaper regions.

Table 2. Light Microscopic Features of Erythrodermic Type of Netherton Syndrome*

Stratum Malpighii Stratum Corneum Thickness of Granules in Stratum Patient No. Hyperkeratosis Parakeratosis Spongiosis Stratum Granulosum Granulosum Cells 1 + +++ +++ − + 2 − ++ ++ − + 3 − + + 2 Layers − 4 − ++ − − − 5+ −− − − 6 ++ − − 2-3 Layers − 7 ++ +++ + 2-3 Layers +

*Plus signs indicate minimal change; double plus signs, moderate change; triple plus signs, maximal change; and minus signs, no difference from normal.

A B

Figure 2. A, Hemotoxylin-eosin staining shows accentuated rete ridges and papillae and absence of the granular layer. Horny layer is completely replaced by parakeratotic cells. Uppermost cells of stratum malpighian are not as flattened as normal, showing irregularly distributed intracellular or extracellular edema and spongiosis of the lower layers. Papillary dermis shows a mild-to-marked inflammatory infiltrate consisting of histiocytes, lymphocytes, and some granulocytes in the perivascular portions. B, Periodic acid-Schiff staining shows focal accumulation of eosinophilic, periodic acid-Schiff–positive, diastase-resisting homogeneous material within parakeratotic stratum corneum and in some regions of the stratum granulosum.

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 parakeratosis. In some regions, follicular hyperkeratosis A SC was evident. The stratum granulation was expanded to 3 to 4 layers, and increased numbers of mitoses were vis- ible in the basal cells. The dermis also showed a variable, patchy perivascular inflammatory infiltrate.21

ELECTRON MICROSCOPY

Control Human Skin

In normal epidermis, exocytosis of LB contents occurred through fusion of the LB-limiting and plasma membranes, almost exclusively limited to the stratum granu- LB losum (SG)/SC interface and subadjacent SG layer.31,32 In the lowermost intercellular spaces of the SC, the secreted LB-derived lamellae began to uncoil within hemi- spherical, saccular dilatations at the SG-SC interface and lower SC (Figure 3, A).24,31 The lateral margins of the B unfurling lamellar membranes at this level seemed loosely connected to adjacent desmosomes.20 Beneath the roof of the same extracellular domains, newly formed, mature lamellar membrane structures formed parallel arrays between neighboring desmosomes. The extracellular domains also displayed a uniform pattern of mature lamellar membrane structures throughout the mid- and upper SC (Figure 3, B).

Netherton Syndrome

Samples from NS displayed a number of features in common (Table 3). Cells in the outer nucleated layers of the epidermis appeared in various stages of transition into corneocytes. Moreover, even when transitional cells were not evident, the SC still appeared less cohesive than in normal SC (ie, they displayed fewer desmosomes and were often separated by elongated clefts) (Figure 4). Individual corneocytes showed numerous intracellular lipid droplets, nuclear remnants, and other inclusions (Figure 4, B). Granular cells were not as flattened as normal, with irregularly distributed intracellular and/or extracellular edema. In edematous regions, keratohyalin granules and keratin filaments also appeared sparser than normal. Moreover, in patients 1, 2, 4, 5, and 7, keratohyalin Figure 3. Normal human skin. A, In normal human skin, exocytosis of granules lacked their characteristic stellatelike shape, lamellar body (LB) lipids into the intercellular spaces (ICS) through fusion of and did not appear to interact normally with tonofibrils; the LB-limiting membrane was completed at the stratum granulosum– stratum corneum (SC) interface. In lower portions of the ICS, LB lipids patients 3 and 6 displayed an SG layered with 2 to 3 assemble into LB sheets. In the upper portion of the same ICS, newly formed cells, with increased numbers of small, globular-shaped lipid layers (arrow) parallel to the roof of the ICS are seen (ϫ325 000, scale keratohyalin granules. Finally, in patients 1 and 2, bar = 0.1 µm). B, In the mid- to upper SC, the ICS shows a lamellar lipid bilayer with desmosomes (ϫ100 000, scale bar = 0.1 µm). spherical, dark cytoplasmic granules, with a diameter varying from 0.3 to 10 µm, were present in the SG cyto- 7,26,27 illary portion of the epidermis was also characteristic, with sol (not shown). anoccasionalpresenceofsmallspongiformpustules.Insome The quantity of LBs in the SG varied greatly. In regions instances, the SC consisted entirely of parakeratotic cells, with severe cytosolic swelling, LBs were conspicuously re- with a concomitant absence of the granular layer. Accumu- duced (Figure 4). In other regions, LBs displayed packed lationsofpyknoticneutrophilswerealsopresentwithinpara- lamellar contents (Figure 5 and Figure 6, D), whereas keratotic areas of the SC (Munro microabscess).30 in other regions, LBs revealed only lamellar fragments. The intercellular spaces at the level of the stratum Congenital Erythrodermic Ichthyosis spinosum and SG were distended in some areas by amorphous, finely granular material (not shown).3,33 In all pa- The epidermis was slightly thickened, with broad rete ridges tients except 1, this material also dilated the extracellu- and a flattened base. The SC was thickened with foci of lar spaces of the overlying SG and SC. (In patient 1, the

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 Table 3. Abnormalities of Barrier Structure in Netherton Syndrome Compared With Other Erythrodermic Conditions*

Normal Skin Netherton Syndrome Psoriatic Erythroderma CIE Lipid secretion At SG-SC interface 3-4 ICS of upper stratum As in normal skin, but also As in normal skin malpighii persistence of LB in the cells Extracellular sheet Simultaneously with lipid Secreted lipids remain Simultaneously with extrusion, Simultaneously with extrusion formation extrusion unprocessed in ICS of upper but look abnormal stratum malpighii Lamellar bilayer LB sheets and bilayers found in Foreshortened LB sheets partly LB sheets are not reorganized Formation of pathologic lipid formation same ICS in stratum filling ICS without into lamellar bilayer layers from LB sheets distribution compactum transformation to regular bilayers ICS of stratum disjunctum Inhibition of bilayer formation Pathological lamellar layers in Irregular widening of ICS with reveal regular bilayers by electron-dense deposits stratum disjunctum excessive numbers of lipid lamellae Lipid layers are separated by Dilatation of ICS by invading Increased number of granular deposits leukocytes, other regions desmosomes and lacunae showing narrow ICS with absence of lipid layers, elongated, pathologic desmosomal structures

*CIE indicates nonbullous congenital ichthyosiform erythroderma; SG, stratum granulosum; SC, stratum corneum; ICS, intercellular spaces; and LB, lamellar body.

granular, intercellular deposits were limited to focal accumulations in the SC.) In some sites, the fine granular material formed a band that separated the SG layer from N a parakeratotic SC. In contrast to CIE and PsoE, LB secretion in NS N occurred not only at the SG-SC interface, but also into the extracellular spaces of 4 or more layers of the subja- cent SG and upper stratum spinosum (Figures 5 and 6). The prematurely secreted lamellar contents remained SC unprocessed for up to 4 layers of the SC (Figures 5 and 6, C and D). In some areas where the cornified envelope was already evident, elongated membrane sheets were present (Figure 6, A and B), but fully processed, mature lamellar membrane structures, such as in nor- N mal skin, did not occur (Figure 3, B). In extracellular domains of the lower SC, fusiform dilatations contained not only LB-derived sheets but also intermingled, electron-dense material, which persisted at and above sites where transformation into mature lamellar membrane structures occurred normally (Figure 7, B and C). The dilatated extracellular spaces of the mid-to- outer SC also displayed focal areas with normal membrane structures (patients 2, 4, and 5) separated by globular, electron-dense material (Figure 7, A), often in the vicinity of desmosomes. Figure 4. Netherton skin. In upper stratum, malpighii keratinocytes appeared in various stages of transition into horny cells. Stratum corneum (SC) lacked Erythrodermic Psoriasis cohesiveness of the normal horny layer, and cells show lipid droplets (arrow), nuclear remnants (N), and numerous inclusions (ϫ4500, scale bar = 10 µm, osmium tetroxide). The SC in PsoE was completely disorganized, showing increased numbers of parakeratotic corneocytes with remnants of nuclei and lipid droplets throughout. The ex- tion of abnormal lipid material, was seen (Figure 8, A). tracellular spaces of the SC were unusually narrow, with The LBs in the cytoplasm of the stratum spinosum and only a few lamellar membranes evident,34 and the ma- SG showed normal structures, with fusion of LBs and the ture pattern of lamellar membrane structures was not ob- cell membrane in the upper 2 layers of the SG, such as served. Desmosomes appeared to be increased in some in normal human epidermis.32 Yet, the elongated LB- parts of the SC and elongated in others (Figure 8, C). derived sheets persisted to higher layers within the SC In sites where neutrophils invaded the SC (Figure 8, A), interstices.35 The cytosol of corneocytes also displayed the formation of intercellular dilatations, with deposi- numerous retained LB remnants.36

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 ally, electron-lucent lacunae surrounded by electron- dense borders were found between the lamellar membranes (Figure 8, D). Although in some regions LBs showed only a few lamellar stacks or ovoid vesicles, other regions showed relatively normal-appearing LBs. Finally, in contrast to NS, extrusion of LB contents was limited to the upper SG and SG-SC interface.

COMMENT

The major function of the epidermis is to form a permeability barrier against excessive loss of bodily fluids. The permeability barrier resides in the SC and derives from the secretion of LB contents that reorganize to form organized arrays of hydrophobic membrane structures. Our ultrastructural study of erythrodermic NS demonstrated marked abnormalities of LB architecture, secretion, and membrane reorganization that likely signify a severe disturbance in permeability barrier function. The frequently observed hypernatremia and dehydration in NS could be explained by a defective barrier that re- sulted in increased loss of free water with reabsorption of solutes.5 Our previous measurements of transepidermal water loss in NS (Table 1, patient 1) also showed a 4-fold increased rate of TEWL compared with a control infant of the same age.17 A severe permeability barrier defect might also explain some unique therapeutic prob- lems in NS, such as the propensity to develop iatrogenic Cushing syndrome40 and aggravation of the dermatosis by retinoid therapy (which helps distinguish NS clinically from other ichthyosiform erythrodermas).6 In addition, failure to thrive in erythrodermic NS could also be ascribed, at least in part, to the barrier defect. A defective barrier would induce epidermal hyperplasia,41 which, if severe and sustained, could induce a high cata- bolic state. As heat is lost through increased surface evapo- ration, energy requirements are increased.42 A defective barrier would increase the tendency to develop skin and systemic infections. Discomfort from pruritus and ero- sions6 could also further increase the caloric drain in these patients. Although severe, recalcitrant hypernatremic dehydration is not uncommon in infantile erythrodermic NS, hypernatremia also occurs in other neonatal erythroder- Figure 5. Netherton skin. Lamellar body disks are found unprocessed in up mas,43 and therefore, this feature alone cannot be con- to 4 intercellular spaces (arrows and arrowhead). No ultrastructurally evident sidered a specific clinical marker for NS. Moreover, eryth- cornified envelope was around cells of the lower layers (ϫ31 000, scale bar = 1 µm, osmium tetroxide). roderma with failure to thrive may be the presenting feature of a number of disorders with diverse causes, including nutritional or metabolic disorders such as cys- Congenital Ichthyosiform Erythroderma tic fibrosis or acrodermatitis enteropathica (deficiency dermatitis)44,45 and immunodeficiency syndromes.15,46,47 As described,34,37-39 the SC in CIE revealed an irregular Therefore, features that could distinguish NS from other distribution of lamellar membranes in the extracellular erythrodermic conditions, especially when there is a de- spaces, with some regions containing excessive num- layed appearance of bamboo hairs, could be crucial for bers of lamellar membranes that displayed an abnormal the timely treatment of such infants.5,6 In this study, we electron-lucent and electron-dense banding pattern. Ex- attempted to identify diagnostically useful ultrastruc- tensive cleft formation also occurred between the lamel- tural features of NS. To date, most ultrastructural stud- lar membranes (Figure 8, D). ies have been within the context of isolated case reports Furthermore, the surfaces of individual corneocytes of NS, either in the erythrodermic27 or in the ILC7,27-29 appeared to be more undulated than normal (Figure 8, B), phenotypes. Moreover, larger series26,33 failed to iden- whereas the corneocyte matrix showed lipid droplets and tify the distinctive features of NS vs other congenital eryth- clefts with longitudinal membrane structures.37 Addition- rodermas. By applying the ruthenium tetroxide method

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D D

Figure 6. Netherton skin. A, Inset of 3 intercellular spaces of Figure 5, with arrow revealing unprocessed lamellar body lipids (ϫ72 000, scale bar = 1 µm, osmium tetroxide). B and C, Ruthenium tetroxide staining shows foreshortened lamellar body sheets in dilatated intercellular spaces (ϫ77 000, scale bar = 1 µm, osmium tetroxide). D, Extruded lamellar body lipids still showing corpuscular arrangement of the lamellar body contents in lower intercellular spaces (D indicates desmosome) (ϫ40 000, osmium tetroxide).

A B

C D

Figure 7. Netherton skin. A, Lamellar lipid bilayers separated by granular, electron-dense material in upper regions of stratum corneum (D indicates desmosomes; ϫ84 000, scale bar = 1 µm, ruthenium tetroxide). B and C, Lamellar body sheet transformation into lamellar lipid layers is disturbed by homogeneous, electron-dense material (B: ϫ7500, scale bar = 1 µm; C: ϫ85 000, scale bar = 1 µm, ruthenium tetroxide). D, Elongated lamellar body sheets were sometimes successfully formed, filling the whole intercellular spaces. However, the same intercellular space domains did not simultaneously show newly formed, mature lipid layers, as was regularly the case in normal skin (ϫ6800, scale bar = 1 µm, ruthenium tetroxide).

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Figure 8. A and C, Psoriasis. A, High number of parakeratotic corneocytes, with remnants of nuclei and lipid droplets (L), appearing distinctly throughout the whole stratum corneum (SC). In areas where neutrophils (G) invaded the SC (upper left nucleus), a widening of intercellular spaces and formation of intercellular lacunae, with accumulations of pathologically structured lipid material, are seen (arrow). C, In the intercellular spaces, pathologic lipid lamellae are seen that show interaction with desmosomes of SC. (A: ϫ12 500, scale bar = 1 µm; C: ϫ50 000, scale bar = 1 µm.) B and D, Congenital erythrodermic ichthyosis. With the ruthenium tetroxide straining method, congenital erythrodermic ichthyosis reveals a normal lamellar body secretory system. B, Survey of the SC shows irregular distribution of lipid membranes, with foci containing excessive numbers of lipid bilayers (ϫ12 500, scale bar = 1 µm). D, Electron-lucent areas (lacunae, arrows) surrounded by electron-dense material were evident (ϫ66 000, scale bar = 1 µm).

in conjunction with osmium tetroxide postfixation, we CIE. Likewise, atopic dermatitis, a disorder that can re- identified certain ultrastructural alterations during the semble NS in neonates, shows delayed and incomplete final stages of epidermal differentiation that could prove LB secretion.32 Even at higher levels of the SC, extracel- both diagnostically useful and functionally significant lular processing of LB-derived sheets into mature lamel- (Table 3). lar membrane unit structures appears to be profoundly First, secretion of LB contents occurs prematurely disturbed in NS. However, these features are not en- and is not followed by timely extracellular processing. tirely specific because lesser but qualitatively similar pro- In normal epidermis, extrusion of LB secretion occurs cessing abnormalities also occur in PsoE and CIE. primarily at the SG-SC interface, followed sequentially The extrusion of LB contents and their subsequent by unfurling and elongation of LB-derived membrane transformation are integrated within a tightly coordi- sheets, which then transform into mature lamellar mem- nated program of normal terminal differentiation,45,48 a brane unit structures in the lower SC.19,20,31 In contrast, sequence that appears to be profoundly disturbed in NS. cornified envelope formation precedes the processing of The reduction in keratin and keratohyalin filaments in LB sheets into mature extracellular lamellae by up to 4 outer nucleated layers of the epidermis suggests that LB SG layers in NS, a feature that is not observed in PsoE or secretion and processing and expression of 1 or more

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©1999 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 structural proteins of epidermal terminal differentiation diagnosis of NS vs other causes of erythrodermas is could be impaired in NS. Recently, a recessive mouse mu- critical, because therapy differs widely. For example, tation with alopecia, abnormal hair (lanceolate hair), and systemic retinoids aggravate NS but can be useful for thickening of the epidermis associated with an ichthyo- other erythrodermic conditions, such as CIE. Correct siform dermatitis was described, and showed similari- diagnosis also directs clinicians to carefully monitor ties to NS.49 Its mutation is located on the centromeric both fluid and electrolyte status and caloric intake in end of chromosome 18, a region homologous to human these patients. 18q12, and bears several candidate genes of epidermal differentiation, including cadherin, desmocollin, and des- Accepted for publication February 26, 1999. moglein.49 Abnormalities of proteins of the desmosomal Corresponding author: Manige´ Fartasch, MD, Depart- plaque might result in defective interactions between cad- ment of Dermatology, University of Erlangen/Nuremberg, herins and keratins (catenin-cadherin complexes are Hartmannstrasse 14, 91052 Erlangen, Germany (e-mail: linked to the actin filament network and to other trans- [email protected]). membrane and cytoplasmic proteins of the cytoskel- 50 eton ). 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Prior studies have shown that extracellular cal- Arch Dermatol. 1969;100:550-558. cium concentrations increase progressively from the basal 5. Traupe H. The Comèl-Netherton Syndrome. In: Traupe H, ed. The Ichthyoses. to the outer SG layer and then decline35,51 and that the Berlin, Germany: Springer-Verlag; 1989:168-178. epidermal calcium gradient regulates LB secretion.52 Thus, 6. Judge MR, Morgan G, Harper JI. A clinical and immunological study of Nether- ton’s syndrome. Br J Dermatol. 1994;131:615-621. impaired formation of the epidermal calcium gradient in 7. Frenk E, Mevorah B. Ichthyosis linearis circumflexa Come`l with trichorrhexis in- 32,51,53-55 NS could account for premature LB secretion and vaginata (Netherton’s syndrome). Arch Dermatol Forsch. 1972;245:42-49. inhibition of terminal differentiation. The calcium gra- 8. Greig D, Wishart J. Growth: abnormality in Netherton’s syndrome. Aust J Der- dient is lost when the barrier is perturbed.51 Severity of matol. 1982;23:27-30. the electrolyte abnormality in some patients with NS also 9. Cambazard F, Thivolet M, Ferrier MC, Mauduit G, Chouvet B, Hermier M. Le syndrome Iroquois: une varainte du syndrome de Netherton? Ann Dermatol Vene- suggests that the primary abnormality might involve ion reol. 1986;113:941-945. channels or pumps. Regardless of the cause of the ab- 10. Platin P, Delaire P, Guillois B, Poinsot J, le Roy J-P, Guillet G. Syndrome de Neth- normal Ca++ gradient, a disturbed gradient could both erton re´ve´lation ne´onatale. Ann Dermatol Venereol. 1989;116:790-792. accelerate the pathogenic features of NS after birth and 11. Shwayerder T, Banerjel S. Netherton syndrome presenting as congenital psoriasis. Pediatr Dermatol. 1997;14:473-476. account for the delayed onset of clinical and ultrastruc- 12. 33 Walravens PA, Hambridge KM, Weston W, Nelder K. Plasma zinc in acroderma- tural disease in some patients. titis enteropathica. Lancet. 1976;1:488. Second, transformation into mature lamellar mem- 13. Bustos JAQ, Gonzales MB. Netherton syndrome, enteropathic acrodermatitis and brane unit structures is disturbed by granular, electron- zinc. Lancet. 1977;2:403-404. dense material. The severe barrier abnormality in NS can 14. Dupre´ A, Bonafe´ JL, Carre`rere S. Ichthyose lineaire circonflexe de Come`l et syndrome de Netherton: conception-Generale. Ann Dermatol Venereol. 1978;105: be explained by premature LB secretion and the exten- 49-54. sive disruption of lamellar processing and organization 15. Jones SK, Thomason LM, Surbrugg SK, Weston WL. Neonatal hypernatremia in observed herein. The amorphous, electron-dense mate- two siblings with Netherton’s syndrome. Br J Dermatol. 1986;114:741-743. rial that forms clefts in NS may form an aqueous pore, 16. Mallory SB, Krafchik BR. What syndrome is this?Pediatr Dermatol. 1992;9:157-160. perhaps explaining why barrier function is more im- 17. Fartasch M. Transepidermal water loss: atopic dermatitis and other skin diseases. In: Elsner P, Berardesca E, Maibach HI, eds. Bioengineering of the Skin: paired in NS than in other disorders of cornification where Water and the Stratum Corneum. Boca Raton, Fla: CRC Press; 1994:87-95. lipids are likely to form the abnormal, nonlamellar phase, 18. Madison KC, Swartzendruber DC, Wertz PW, Downing DT. Presence of intact eg, Refsum disease, Sjo¨gren-Larsson syndrome,56 and neu- intercellular lipid lamellae in the upper layers of the stratum corneum. J Invest tral lipid storage disease.57 The interaction of desmo- Dermatol. 1987;88:714-718. somes (corneosomes) within the SC with lamellar mem- 19. Hou SYE, Mitra AK, White SH, Menon GK, Ghadially R, Elias PM. Membrane structure in normal and essential fatty acid-deficient stratum corneum: characteriza- brane structures is also disturbed by the accumulation tion by ruthenium tetroxide staining and X-ray diffraction. J Invest Dermatol. 1991; of excess electron-dense material in NS (Figure 6). This 96:215-223. pathologic interaction might be responsible for the spe- 20. Fartasch M, Bassukas ID, Diepgen TL. Structural relationship between epider- cific clinical feature of desquamation observed in ILC mal lipid lamellae, lamellar bodies and desmosomes in human epidermis: an ultrastructural study. Br J Dermatol. 1993;128:1-9. (double-edged scale). 21. Williams ML, Elias PM. Heterogeneity in autosomal recessive ichthyosis: clini- In summary, the ultrastructural findings of the epi- cal and biochemical differentiation of lamellar ichthyosis and nonbullous con- dermal barrier components shown for NS are not genital ichthyosiform erythroderma. Arch Dermatol. 1986;121:477-488. observed in other congenital erythrodermic skin disor- 22. Choate KA, Williams ML, Khavari PA. An abnormal transglutaminase 1 expres- ders (PsoE and CIE) that share clinical features in early sion pattern in a subset of patients with erythrodermic autosomal recessive ichthyosis. J Invest Dermatol. 1998;110:8-12. infancy. We suggest, therefore, that the ultrastructural 23. Huber M, Arnold M-L, Anton-Lamprecht I, Hohl D. Correlation between trans- features described might assist in the early diagnosis of glutaminase defect and ultrastructural markers in lamellar ichthyosis [abstract]. NS, leading to improved survival of these patients. Early J Invest Dermatol. 1997;108:644.

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News and Notes

he Cleveland Clinic Foundation Dermatopathol- ogy Self-Assessment Workshop will be held on T October 2, 1999 at the Renaissance Hotel. The course director is Wilma F. Bergfeld, MD, Head of the Section of Dermatopathology, Departments of Dermatology and Pathology. For more information Contact Wilma F. Bergfeld, MD, Department of Dermatology A61, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195; phone: (216) 444-5722; fax: (216) 231-5448.

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