Recessive ichthyosis congenita type II

Autosomal recessive congenital ichthyosis

The term autosomal recessive congenital ichthyosis (ARCI) refers to a group of rare disorders of keratinization classified as nonsyndromic forms of ichthyosis. This group was traditionally divided into lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE) but today it also includes harlequin ichthyosis, self-healing collodion baby, acral self-healing collodion baby, and bathing suit ichthyosis. The combined prevalence of LI and CIE has been estimated at 1 case per 138 000 to 300 000 population. In some countries or regions, such as Norway and the coast of Galicia, the prevalence may be higher due to founder effects. ARCI is genetically highly heterogeneous and has been associated with 6 genes to date: TGM1, ALOXE3, ALOX12B, NIPAL4, CYP4F22, and ABCA12. In this article, we review the current knowledge on ARCI, with a focus on clinical, histological, ultrastructural, genetic, molecular, and treatment-related aspects.

Revised nomenclature and classification of inherited ichthyoses: results of the First Ichthyosis Consensus Conference in Sorèze 2009

BACKGROUND

Inherited ichthyoses belong to a large, clinically and etiologically heterogeneous group of mendelian disorders of cornification, typically involving the entire integument. Over the recent years, much progress has been made defining their molecular causes. However, there is no internationally accepted classification and terminology.

OBJECTIVE

We sought to establish a consensus for the nomenclature and classification of inherited ichthyoses.

METHODS

The classification project started at the First World Conference on Ichthyosis in 2007. A large international network of expert clinicians, skin pathologists, and geneticists entertained an interactive dialogue over 2 years, eventually leading to the First Ichthyosis Consensus Conference held in Sorèze, France, on January 23 and 24, 2009, where subcommittees on different issues proposed terminology that was debated until consensus was reached.

RESULTS

It was agreed that currently the nosology should remain clinically based. "Syndromic" versus "nonsyndromic" forms provide a useful major subdivision. Several clinical terms and controversial disease names have been redefined: eg, the group caused by keratin mutations is referred to by the umbrella term, "keratinopathic ichthyosis"-under which are included epidermolytic ichthyosis, superficial epidermolytic ichthyosis, and ichthyosis Curth-Macklin. "Autosomal recessive congenital ichthyosis" is proposed as an umbrella term for the harlequin ichthyosis, lamellar ichthyosis, and the congenital ichthyosiform erythroderma group.

LIMITATIONS

As more becomes known about these diseases in the future, modifications will be needed.

CONCLUSION

We have achieved an international consensus for the classification of inherited ichthyosis that should be useful for all clinicians and can serve as reference point for future research.

[Cutaneous fissures in collodion babies: incidence and treatment]

BACKGROUND

Collodion baby syndrome (CBS) is a pathological cutaneous condition present at birth and is due to the presence of a thick horny layer of the skin. Exfoliation begins early with drying and cracking of the collodion membrane. The cracks may either remain superficial or they may be deeper and affect the superficial dermis, in which case, fissures form. This study of CBS provides information on the clinical aspect of fissures, their incidence, their pathological consequences and therapeutic approaches.

PATIENTS AND METHODS

In our study, diagnosis of CBS was made clinically based on the presence of neonatal collodion membrane. Identification of typical cracks and fissures was made on clinical examination and their site, chronology and consequences were assessed. Routine bacteriological examination of fissures was performed twice weekly on a clinically infected specimen taken from an inguinal fissure. The therapeutic protocol for CBS has been validated and involved use of sterile vaseline oil. Fissures were disinfected.

RESULTS

Cracks are a constant feature. Fissures were seen in 20 of the 33 cases of CBS with the site of predilection being large skinfolds. Morphine was necessary for pain relief in three cases. Pathogenic organisms were isolated in all cases of inflammatory fissures. Dissemination of septicaemia was confirmed in four cases and the offending organism was isolated from the inflammatory fissures in all cases. Candida albicans was present in all cases of fissures in the inguinal folds or between the buttocks. Keratotic adhesions occurred after healing of digital fissures and a surgical procedure was required in this event.

DISCUSSION

Fissures are lesions occurring secondarily to cracks and they were seen in 20 of the 33 cases of CBS. These secondary lesions are rarely mentioned in the literature and the reasons for this oversight are discussed. Fissures are potential complications in all states of CBS, particularly where the collodion is thick. Topical treatment does not prevent transformation of cracks to fissures in all cases. Where fissures are not inflammatory, routine prescription of oral antibiotics is not always necessary. Regular bacteriological monitoring at several different fissure sites allows selection of appropriate antibiotic therapy. The main therapeutic goal in CBS is to treat painful fissures and superinfection.

Congenital ichthyosis: mutations in ichthyin are associated with specific structural abnormalities in the granular layer of epidermis

BACKGROUND

Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of skin disorders. Several mutant genes have been identified in ARCI, but the association between genotype and phenotype is poorly understood.

METHODS

To investigate genotype-phenotype correlations in ARCI, we selected 27 patients from 18 families with specific ultrastructural features of the epidermis. The characteristic findings using electron microscopy (EM) were abnormal lamellar bodies and elongated membranes in the stratum granulosum, classified as ARCI EM type III. DNA samples from a subset of affected individuals were screened for homozygous genomic regions, and a candidate gene region was identified on chromosome 5q33. The region coincides with the ichthyin gene, previously reported as mutated in ARCI.

RESULTS

Mutation screening of ichthyin revealed missense or splice-site mutations in affected members from 16 of 18 (89%) families with characteristics of ARCI EM type III. In a control group of 18 patients with ARCI without EM findings consistent with type III, we identified one patient homozygous for a missense mutation in ichthyin.

DISCUSSION

Our findings indicate a strong association between ultrastructural abnormalities in the granular layer of epidermis and ichthyin mutations. The results also suggest that EM provides a tool for specific diagnosis in a genetically homogenous subgroup of patients with ARCI.

The skin barrier in healthy and diseased state

The primary function of the skin is to protect the body for unwanted influences from the environment. The main barrier of the skin is located in the outermost layer of the skin, the stratum corneum. The stratum corneum consists of corneocytes surrounded by lipid regions. As most drugs applied onto the skin permeate along the lipid domains, the lipid organization is considered to be very important for the skin barrier function. It is for this reason that the lipid organization has been investigated quite extensively. Due to the exceptional stratum corneum lipid composition, with long chain ceramides, free fatty acids and cholesterol as main lipid classes, the lipid organization is different from that of other biological membranes. In stratum corneum, two lamellar phases are present with repeat distances of approximately 6 and 13 nm. Moreover the lipids in the lamellar phases form predominantly crystalline lateral phases, but most probably a subpopulation of lipids forms a liquid phase. Diseased skin is often characterized by a reduced barrier function and an altered lipid composition and organization. In order to understand the aberrant lipid organization in diseased skin, information on the relation between lipid composition and organization is crucial. However, due to its complexity and inter-individual variability, the use of native stratum corneum does not allow detailed systematic studies. To circumvent this problem, mixtures prepared with stratum corneum lipids can be used. In this paper first the lipid organization in stratum corneum of normal and diseased skin is described. Then the role the various lipid classes play in stratum corneum lipid organization and barrier function has been discussed. Finally, the information on the role various lipid classes play in lipid phase behavior has been used to interpret the changes in lipid organization and barrier properties of diseased skin.

The clinical spectrum of nonbullous congenital ichthyosiform erythroderma and lamellar ichthyosis

Until about 20 years ago, the term lamellar ichthyosis (LI) represented all nonbullous autosomal recessive ichthyoses except for harlequin ichthyosis and ichthyosis syndromes. Since the 1980s, nonbullous autosomal recessive ichthyoses have been divided into two major clinical entities, nonbullous congenital ichthyosiform erythroderma (NBCIE) and LI. The nature of scaling and intensity of erythroderma are important clinical features that distinguish between NBCIE and LI. However, a considerable number of cases show an intermediate phenotype between the two classic clinical features. Histologically, parakeratosis and inflammatory cell infiltration are seen more frequently in NBCIE than in LI and the stratum corneum is usually thicker in LI than in NBCIE. However, neither histopathological findings nor ultrastructural features seem to help clearly distinguish between NBCIE and LI. Mutations in any of the three known causative genes, TGM1, ALOXE3 or ALOX12B, can lead either to NBCIE or LI. Candidate genes specific to either NBCIE or LI alone have not been identified. Based on these facts, it might be better to consider NBCIE and LI as variations of a single keratinization disorder, although the classification of these autosomal recessive congenital ichthyosis patients into NBCIE or LI depending on their clinical features is still useful for practical patient management.

Development of ichthyosiform skin compensates for defective permeability barrier function in mice lacking transglutaminase 1

Transglutaminase 1 (TGase 1) is one of the genes implicated in autosomal recessive congenital ichthyosis. Skin from TGase 1(-/-) mice, which die as neonates, lacks the normal insoluble cornified envelope and has impaired barrier function. Characterization of in situ dye permeability and transepidermal water loss revealed defects in the development of the skin permeability barrier in TGase 1(-/-) mice. In the stratum corneum of the skin, tongue, and forestomach, intercellular lipid lamellae were disorganized, and the corneocyte lipid envelope and cornified envelope were lacking. Neonatal TGase 1(-/-) mouse skin was taut and erythrodermic, but transplanted TGase 1(-/-) mouse skin resembled that seen in severe ichthyosis, with epidermal hyperplasia and marked hyperkeratosis. Abnormalities in those barrier structures remained, but transepidermal water loss was improved to control levels in the ichthyosiform skin. From these results, we conclude that TGase 1 is essential to the assembly and organization of the barrier structures in stratified squamous epithelia. We suggest that the ichthyosiform skin phenotype in TGase 1 deficiency develops the massive hyperkeratosis as a physical compensation for the defective cutaneous permeability barrier required for survival in a terrestrial environment.

Aberrant lipid organization in stratum corneum of patients with atopic dermatitis and lamellar ichthyosis

There are several skin diseases in which the lipid composition in the intercellular matrix of the stratum corneum is different from that of healthy human skin. It has been shown that patients suffering from atopic dermatitis have a reduced ceramide content in the stratum corneum, whereas in the stratum corneum of lamellar ichthyosis patients, the amount of free fatty acids is decreased and the ceramide profile is altered. Both patient groups also show elevated levels of transepidermal water loss indicative of an impaired barrier function. As ceramides and free fatty acids are essential for a proper barrier function, we hypothesized that changes in the composition of these lipids would be reflected in the lipid organization in stratum corneum of atopic dermatitis and lamellar ichthyosis patients. We investigated the lateral lipid packing using electron diffraction and the lamellar organization using freeze fracture electron microscopy. In atopic dermatitis stratum corneum, we found that, in comparison with healthy stratum corneum, the presence of the hexagonal lattice (gel phase) is increased with respect to the orthorhombic packing (crystalline phase). In lamellar ichthyosis stratum corneum, the hexagonal packing was predominantly present, whereas the orthorhombic packing was observed only occasionally. This is in good agreement with studies on stratum corneum lipid models that show that the presence of long-chain free fatty acids is involved in the formation of the orthorhombic packing. The results of this study also suggest that the ceramide composition is important for the lateral lipid packing. Finally, using freeze fracture electron microscopy, changes in the lamellar organization in stratum corneum of both patient groups could be observed.

Ultrastructural features resembling those of harlequin ichthyosis in patients with severe congenital ichthyosiform erythroderma

Congenital ichthyoses are a group of heterogeneous disorders of cornification. Autosomal recessive congenital ichthyosis (ARCI) can be clinically subdivided into congenital ichthyosiform erythroderma and lamellar ichthyosis. Ultrastructurally, ARCI is classified into four groups: ichthyosis congenita (IC) types I-IV. The genetic background of the ARCI disorders is heterogeneous, but only one disease gene, transglutaminase 1, has been detected so far. We describe six patients with severe congenital ichthyosis from six different Scandinavian families. They could not be classified ultrastructurally into the four IC groups because of atypical findings of electron microscopy. These included abnormal lamellar bodies, alterations in keratohyalin, remnant organelles and lipid inclusions in the upper epidermal cells, which resembled the ultrastructural findings of harlequin ichthyosis (HI), although the HI phenotype was not present at birth. Some clinical features, such as thick scales, erythroderma, alopecia and ectropion were common to all patients. Ichthyosis was usually accentuated in the scalp and four patients had clumped fingers and toes. None of the patients carried the transglutaminase 1 mutation. We conclude that ultrastructural findings resembling those detected in previous HI cases (type 1 and 2) can also be found in patients who do not have classic clinical features of that rare ichthyosis. This may be due to lack of specificity of ultrastructural markers for HI or to its clinical heterogeneity.

Analyses of the transglutaminase 1 gene mutation and ultrastructural characteristics in a Japanese patient with lamellar ichthyosis

We described a Japanese female with lamellar ichthyosis whose transglutaminase 1 gene (TGM1 gene) was mutated. DNA sequence analysis revealed that the patient had a homozygous mutation, i.e. a point mutation from G to A at nucleotide 1494 resulting in the substitution of glycine for arginine at codon 143. Her mother was heterozygous for this mutation. In situ transglutaminase assay in the patient's skin showed loss of enzyme activity. Ultrastructural examination revealed incomplete formation of cornified cell envelopes and electron-dense materials adjacent to plasma membranes. These results suggest that defective transglutaminase activity caused by homozygous TGM1 gene mutation (G143R) results in disruption of cornified envelope assembly and the clinical phenotype of lamellar ichthyosis.

Eyelid abnormalities in lamellar ichthyoses

PURPOSE

To describe eyelid abnormalities in lamellar ichthyoses (LI).

DESIGN

Retrospective observational case series.

PARTICIPANTS

Eight patients with classic LI and two patients with congenital ichthyosiform erythroderma.

METHODS

Results of eyelid and corneal examinations of 10 patients with LI were reviewed and analyzed with emphasis on the relationship between eyelid ectropion and corneal damage.

RESULTS

All patients presented with cicatricial lagophthalmos. Of the eight patients with classic LI, five had ectropion of the four eyelids, one had only lower ectropion, and two had no degree of ectropion. Two patients with congenital ichthyosiform erythroderma had distinct eyelid abnormalities, including madarosis and eyelash retraction. Loss of vision caused by corneal damage was found in three patients with classic LI. Of these three patients, two did not have upper eyelid ectropion.

CONCLUSIONS

Severe corneal damage can occur in LI even if there is no upper or lower eyelid ectropion.

Defective stratum corneum and early neonatal death in mice lacking the gene for transglutaminase 1 (keratinocyte transglutaminase)

The stratum corneum of the skin serves as an effective barrier for maintenance of the internal milieu against the external environment. At the cell periphery of the stratum corneum is the cell envelope, a highly insoluble membranous structure composed of precursor proteins cross-linked by epsilon-(gamma-glutamyl)lysine bonds. Transglutaminase 1 (TGase 1; keratinocyte TGase), a membrane-bound isozyme of the TGase family, has been proposed to catalyze this process of assembly. Deficient cross-linking of the cell envelope in some patients with the autosomal recessive skin disorder lamellar ichthyosis (LI) and several mutations of the TGase 1 gene that have been identified in families with LI suggest the importance of this gene in production of the cell envelope. In this study, we generated mice lacking the TGase 1 gene, and we report that they have erythrodermic skin with abnormal keratinization. In their stratum corneum, degradation of nuclei and keratohyalin F-granules was incomplete and cell envelope assembly was defective. The skin barrier function of TGase 1-null mice was markedly impaired, and these mice died within 4-5 h after birth. These results clearly demonstrate that the TGase 1 gene is essential to the development and maturation of the stratum corneum and to adaptation to the environment after birth. Thus, these TGase 1 knockout mice may be a useful model for severe cases of LI.

Structural organization of cornified cell envelopes and alterations in inherited skin disorders

The cornified cell envelope is a highly insoluble and extremely tough structure formed beneath the cell membrane during terminal differentiation of keratinocytes. Its main function is to provide human skin with a protective barrier against the environment. Sequential cross-linking of several integral components catalyzed by transglutaminases leads to a gradual increase in the thickness of the envelope and underscores its rigidity. Key structural players in this cross-linking process include involucrin, loricrin, SPRRs, elafin, cystatin A, S100 family proteins, and some desmosomal proteins. The recent identification of genetic skin diseases with mutations in the genes encoding some of these proteins, including transglutaminase 1 and loricrin, has disclosed that abnormal cornified cell envelope synthesis is significantly involved in the pathophysiology of certain inherited keratodermas and reflects perturbations in the complex, yet highly orderly process of cornified cell envelope formation in normal skin biology.

Collodion baby and lamellar ichthyosis

It is important to differentiate the collodion baby from harlequin ichthyosis as the latter rarely survives past the first few days of life. Occasionally, babies share features of both disorders and defy a clinical diagnosis. We recently encountered such a baby who initially presented with harlequin-like features, but evolved into lamellar ichthyosis once the keratin cast was shed. Since the routine histology of all these ichthyoses is similar, we used electron microscopy to study serial biopsy specimens from the affected infant on days 7, 14, and 150, and compared them to our own other cases of harlequin ichthyosis and lamellar ichthyosis. Electron microscopic studies of our case revealed that the marginal band of cornified cells of the stratum corneum was absent when the baby exhibited collodion/harlequin ichthyosis features. Another biopsy taken when the clinical picture evolved into lamellar-like ichthyosis, showed a well-formed marginal band in the cornified cells. In harlequin ichthyosis, the marginal band is present at birth. It is suggested that electron microscopy can differentiate severe collodion baby from harlequin ichthyosis at birth using the absence of the marginal band. Previously reported features of harlequin ichthyosis, such as the presence of giant mitochondria and an abnormal formation of the marginal band in luminal villi of acrosyringeal eccrine duct, were absent in our case.

Inability of keratinocytes lacking their specific transglutaminase to form cross-linked envelopes: absence of envelopes as a simple diagnostic test for lamellar ichthyosis

Epidermal keratinocytes, late in their terminal differentiation, form cross-linked envelopes resistant to ionic detergent and reducing agent. Because the cross-linking process is catalyzed by the keratinocyte transglutaminase, the absence of active transglutaminase should result in failure of the keratinocyte to form a cross-linked envelope. Three keratinocyte strains bearing mutations in the keratinocyte transglutaminase were examined: two contained no detectable transglutaminase mRNA and none contained active enzyme. All three were unable to form cross-linked envelopes, either spontaneously in stratified cultures or upon induction with Ca2+. Although stratum corneum of normal humans and scales from patients with different ichthyotic diseases contain cross-linked envelopes, those from patients with transglutaminase-negative lamellar ichthyosis do not. Therefore, the disease due to the absence of transglutaminase may be readily distinguished from other ichthyotic disease by a simple test for cross-linked envelopes.

Cornified cell envelope proteins and keratins are normally distributed in harlequin ichthyosis

Long-term survivors of harlequin ichthyosis (HI) have raised a controversy over the differences between HI and lamellar ichthyosis (LI). Abnormal lamellar granules and the failure of conversion from profilaggrin to filaggrin have been reported in HI. On the other hand, malformation of the cornified cell envelope as a result of mutation of keratinocyte transglutaminase has been found in LI. In the present study, we analyzed the distribution of keratins, filaggrin/profilaggrin and cornified cell envelope proteins in the epidermis in HI. We studied a newborn Japanese male with typical clinical features of HI. Electron microscopic observation of a skin biopsy specimen taken from the trunk revealed the presence of lipid inclusions within the cornified cells, the absence of lamellar granules in the granular layer keratinocytes, and a lack of extracellular lamellar structures between the first cornified cell and the granular cell. Immunohistochemical labeling showed a normal distribution of keratins (keratins 1, 5, 10, and 14), filaggrin/profilaggrin and cornified cell envelope proteins (involucrin, small proline-rich proteins, and loricrin) in the epidermis of lesional skin. The present observations of the patient's skin verified that keratins and cornified cell envelope proteins are normally expressed in HI, thus demonstrating a different pathogenesis between HI and LI.

Reduced skin barrier function parallels abnormal stratum corneum lipid organization in patients with lamellar ichthyosis

Most patients with autosomal recessive lamellar ichthyosis are known to have markedly impaired skin barrier function. We hypothesize that this may be due to imperfections in the composition and fine structure of the intercellular stratum corneum lipids. The aim of the present study was to test this hypothesis. To characterize the barrier properties in three female patients with lamellar ichthyosis, the following parameters were used and compared with those of healthy volunteers: transepidermal water loss, stratum corneum lipid profiles after topical acetone/ether extraction on the flexure side of the forearm, and small-angle x-ray diffraction. The extracted lipids were separated using high performance thin-layer chromatography and quantified, and the ceramide profile was determined. Small-angle x-ray diffraction was used to obtain information on the molecular structure and organization of the intercellular lipid domains of stratum corneum using stratum corneum scales collected by scraping. Transepidermal water loss was significantly increased in all three patients. Lipid analysis showed significant differences in the relative amounts of ceramide fractions 2-3a-3b-4-5, free fatty acid-ceramide ratio, and free fatty acid-cholesterol ratio. Small-angle x-ray diffraction showed smaller repeated distances of lipid bilayers in stratum corneum samples of the patients compared with the healthy volunteers. An additional diffraction peak was found in the patients compared with the healthy volunteers, which can be ascribed to crystalline cholesterol. These data suggest that there might be a relation between the impaired barrier function and stratum corneum lipid structural and composition changes.

Pityriasis rotunda: report of a familial occurrence and review of the literature

Pityriasis rotunda is an uncommon dermatosis characterized by multiple, widely distributed, strikingly circular hypopigmented or hyperpigmented patches that are slightly scaly. It has been described in Oriental and black patients, usually in association with certain infective or malignant systemic diseases. Pityriasis rotunda is rare in white patients and does not act as a marker of malignancy. Our ultrastructural and histologic findings demonstrated that pityriasis rotunda is more closely related to congenital ichthyoses than ichthyosis vulgaris, contrary to previous reports. On the basis of our studies and a review of the literature, it seems that two types of pityriasis rotunda exist with significant prognostic differences.

Clinical, light and electron microscopic features of recessive congenital ichthyosis type I

Based on electron microscopic features, recessive congenital ichthyoses have recently been divided into four subgroups designated ichthyosis congenita (IC) types I, II, III and IV. Type II is characterized by cholesterol clefts in the horny cells, type III by perinuclear elongated membranes in the granular and horny cells, and type IV by masses of lipid membranes in granular and horny cells. Clear electron microscopic criteria for type I are lacking, although the presence of lipid droplets in the horny cells has been suggested as a criterion. In the present study we included ichthyosis patients with (i) recessive inheritance, (ii) erythrodermic fine scaling, (iii) lack of fine structural markers of IC types II-IV. Patients with ichthyotic syndromes were excluded. The case material consisted of 21 patients from 14 families. Eight were collodion babies at birth, but three were normal. Nine had ectropion, the flexures were affected in 12, and the palms and soles were thickened in all but one patient. On electron microscopy lipid vacuoles in the horny cells were common, but were absent in four patients. Changes in other lipid-related structures, including keratinosomes, were common. We conclude that currently type I can be diagnosed only by excluding the other types of ichthyosis. Clinically, IC type I corresponds to classical non-bullous congenital ichthyosiform erythroderma, but there is marked heterogeneity among affected individuals.

Histological and ultrastructural study of a family with erythrokeratodermia progressiva symmetrica

We have examined a family with 4 members in three succeeding generations suffering from a severe keratinization disorder. The clinical phenotype, with symmetric plaques on the extremities, corresponded to erythrokeratodermia progressiva symmetrica. It was manifested at birth, however, and in addition to the hyperkeratotic plaques, follicular hyperkeratosis was also observed. Electron microscopy revealed multiple morphological changes such as myelinated membrane structures, or needles, which were similar to those occurring in ichthyotic disorders and tyrosinemia, as well as in harlequin fetuses, all of which were excluded clinically or biochemically in our patients.

Mitotic Langerhans cell as a possible sign of activation in ichthyosis

The fine structure of Langerhans cells (LC) in four rare types of ichthyosis, namely recessive ichthyosis congenita type II, III and IV and ichthyosis hystrix Curth-Macklin was examined. Signs of LC activation were observed in eight of 21 patients. In IC type IV, the rare occurrence of a mitotic LC was observed. It is possible that LCs are secondarily activated in keratinization disorders.

Membrane structural abnormalities in the stratum corneum of the autosomal recessive ichthyoses

Congenital ichthyosiform erythroderma (CIE) and classic lamellar ichthyosis (LI) are autosomal recessive disorders of cornification (DOC), distinguished previously by clinical, histologic, ultrastructural, and cell kinetic criteria. Whether there is further heterogeneity within the CIE group is uncertain. To address the issue of genetic heterogeneity, and to study the pathogenesis of these DOC, skin biopsies from eight CIE, three LI, and six normal subjects were assessed by electron microscopy, including ruthenium tetroxide postfixation with optical diffraction, to visualize and quantitate intercellular membrane domains. We found abnormal lamellar bodies in CIE and distinctive alterations in intercellular lamellar bilayer architecture among patients with CIE and three patients with LI. Two biopsies from two patients at different sites demonstrated the consistency of these findings. Moreover, in both CIE and the three LI patients, desmosomes persisted throughout the outer layers of the SC, indicative of impaired degradation. Our ultrastructural observations support the previously reported phenotypic distinction between CIE and LI, and the further likelihood of genetic heterogeneity within CIE. However, these studies do not support the division of the autosomal recessive ichthyoses into three subgroups based upon cytosolic structural abnormalities. Finally, these studies provide new insights into the pathogenesis of the autosomal recessive DOC.

Clinical, light and electron microscopic features of recessive ichthyosis congenita type III

The recessively inherited congenital ichthyoses have ultrastructural features which indicate abnormal epidermal lipid metabolism. The ultrastructural markers of the three recessive congenital ichthyosis groups are lipid droplets in horny layers (type I), cholesterol clefts (type II) and membrane structures (type III). We describe six patients from five families belonging to the last group. The variable clinical phenotype alone does not allow the delineation of this disease, but together with the ultrastructural characteristics the subtype is unequivocal. In addition to the membrane structures, half of the cases showed abnormal keratinosomes and vesicular complexes. Membrane-bound vacuoles and needle-like slits were exceptionally found. The onset of the ichthyosis was variable, in contrast to other patients described under the heading recessive congenital ichthyosis.