Stratum corneum hydration and flexibility are useful parameters to indicate clinical severity of congenital ichthyosis

To determine any correlation between the stratum corneum barrier function and the phenotypic severity of congenital ichthyosis, we studied stratum corneum hydration, flexibility, thickness and transepidermal water loss (TEWL) in patients with congenital ichthyosis. Seven patients with congenital ichthyosis aged 2-46 years and age-matched controls were included in the present study. We divided seven patients into two groups; patients with non-bullous type (non-bullous congenital ichthyosiform erythroderma patients) and patients with the bullous type of congenital ichthyosis (bullous congenital ichthyosiform erythroderma and ichthyosis bullosa of Siemens). Stratum corneum hydration, thickness and flexibility were measured using a Corneometer ASA-M2. The stratum corneum thickness was also examined using a skin biopsy technique. TEWL was measured using Evaporimeter AS-TW1. The clinical severity of ichthyosis phenotype was evaluated using a visual analogue scale (VAS). Stratum corneum hydration and flexibility were significantly reduced in both congenital ichthyosis patient groups. Stratum corneum thickness was significantly increased in both groups. In the patient group with non-bullous congenital ichthyosis, significant negative correlations were confirmed between the VAS score and stratum corneum hydration and between the VAS score and flexibility. A significant, positive correlation was also observed between the VAS score and stratum corneum thickness. There was a positive correlation between the VAS score and TEWL on both the extensor and flexor sides of the forearm and back. We conclude that stratum corneum hydration, flexibility and thickness measured by the corneometer, and TEWL on the arm may be a useful indicator of the severity of ichthyosis phenotype.     

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.     

The fibrous proteins in various types of ichthyosis.

The stratum corneum of individuals with ichthyosis vulgaris, sex-linked ichthyosis, lamellar ichthyosis, and epidermolytic hyperkeratosis has been studied. An alpha x-ray diffraction pattern has been observed in all specimens and the solubility of the alpha fibrous proteins appears to be the same as in normal stratum corneum. Sodium dodecyl sulfate (SDS)-polyacrylamide electrophoresis of the fibrous proteins showed variable patterns within the different types of ichthyosis, while amino acid analyses of the proteins were quite similar to those from normal stratum corneum. These data suggest that the fibrous proteins in the ichthyosis are not abnormal, but further studies on the individual polypeptide chains are necessary to rule out more subtle differences.     

The Keratinization Disorder in Collodion Babies Evolving into Lamellar Ichthyosis*

Two collodion baby girls with disorder evolving into lamellar ichthyosis were followed by light and electron microscopy. Light microscopically, the neonatal collodion skin was characterized by a thick compact stratum corneum which was PAS positive in its upper two thirds, by a thin stratum granulosum and by a non-acanthotic stratum spinosum with normal mitotic activity. Electron microscopically, the upper stratum corneum appeared pathological, whereas the lower part was normal except for some minor parakeratosis. The main alterations in the underlying stratum granulosum were diminished tonofibrils and keratohyalin. Biopsy specimens taken at the age of 2 weeks were typical for lamellar ichthyosis and showed hyperkeratosis with focal parakeratosis, a thickened stratum granulosum in which the cellular content of keratohyalin and tonofibrils was moderately diminished, and acanthosis with increased mitotic activity. It appears that the ultrastructural changes of the stratum granulosum, seen in lamellar ichthyosis, are already present in the collodion skin of the newborn, at a time when the epidermis does not yet show an increase in mitotic activity.     

The content of free amino acids in the stratum corneum is increased in senile xerosis

Xerosis is one of the characteristics of aged skin. Xerosis may be caused by a decrease in the stratum corneum free amino acids which are natural moisturizing factors derived from filaggrin. In aged skin, filaggrin is immunohistochemically decreased compared with the levels in young skin. However, the differences in stratum corneum amino acids between aged and young skin have not been analyzed quantitatively. Therefore, in this study we determined the stratum corneum amino acids per 1000 stratum corneum cells in aged and young skin by high-performance liquid chromatography. The amount of filaggrin mRNA in the epidermis was also compared between aged and young skin using RT-PCR. The total amount of amino acids in the stratum corneum was larger in aged senile xerosis skin than in young skin. Only a few amino acids were found in the stratum corneum of ichthyosis vulgaris patients (control skin). The expression of filaggrin mRNA in aged skin was, however, similar to that in young skin. These findings suggest that the immunohistochemical decrease in filaggrin in aged skin may be caused by promotion of filaggrin proteolysis in the upper layers of the stratum spinulosum.     

Stereological studies of desmosomes in ichthyosis vulgaris

Standardized stereological methods were performed on biopsies from three subjects with normal skin and from three patients with autosomal dominant and three with autosomal recessive sex-linked ichthyosis to determine the relative numbers and dimensions of desmosomes. The results showed an increase in the persistence of desmosomes in the stratum corneum in both ichthyotic groups. This suggests a pathogenetic role for desmosomes in the abnormal desquamation of the two types of ichthyosis vulgaris.     

Ichthyosis: Mechanisms of Disease

The disorders of cornification (ichthyoses) comprise acquired and inherited disorders characterized clinically by generalized scaling and histologically by hyperkeratosis. They may arise through defects in the production or maintenance of a normal cornified cell compartment, or both. The stratum corneum is composed of protein-enriched and lipid-depleted corneocytes ("bricks") surrounded by an intercellular domain ("mortar") composed of hydrophobic, lipid-enriched membrane bilayers, and containing desmosomes and a limited array of hydrolytic enzymes. Mechanisms whereby a genetic defect involving either the bricks or the mortar may result in abnormal stratum corneum retention are discussed using ichthyosis vulgaris and recessive X-linked ichthyosis as examples. In addition, epidermal hyperproliferation, which floods the cornified cell compartment with incompletely formed units, results in hyperkeratosis. To date, no primary disorders of epidermal hyperproliferation have been defined. Recent work, however, demonstrates that stratum corneum barrier function regulates epidermal DNA synthesis. For example, in essential fatty acid deficiency, barrier dysfunction is responsible at least in part ror the epidermal hyperproliferation. Defective barrier function due to defective lamellar body secretion may also underlie the phenotypic changes after birth in harlequin ichthyosis; that is, from the massive, constrictive hyperkeratosis of the newborn to an exfoliative erythroderma in survivors. The mechanisms whereby specific defects in cornification result in generalized scaling disease are only beginning to be defined. Yet, even at this early stage, the view of the stratum corneum as a tightly organized structure whose function is highly regulated is emerging. Hence, the disorders of cornification should provide important insights into stratum corneum structure and function.     

Palmoplantar keratoderma with an unusual composition of stratum corneum and serum sterol derivatives: a new entity?

Summary Little is known about the aetiology and pathogenesis of the different types of inherited and acquired palmoplantar keratodermas. We describe a condition of painful palmoplantar keratoderma with an altered stratum corneum lipid pattern which may be responsible for the excessive cornilication. Plantar stratum corneum lipids were analysed by quantitative thin-layer chromatography. Serum lipids, and the activities and gene loci of the enzymes serum steroid sulphatase and arylsulphatase C were also determined. Examination revealed that both the stratum corneum and the serum cholesterol sulphate (CS) content were significantly elevated in comparison with the stratum corneum cholesterol ester content. The cholesterol content was unchanged compared with controls. Serum activities of steroid sulphatase and arylsulphatase C were decreased, but not to the extent found in recessive X-linked ichthyosis. Their gene loci did not show any deletions.
This unique distribution of stratum corneum sterol derivatives, reflected by the elevated serum CS concentration, may contribute to the altered structural and functional properlies of intercellular lipid lamellae within the stratum corneum of this type of keratoderma.     

Harlequin ichthyosis with epidermal lipid abnormality.

An infant with phenotypic harlequin ichthyosis survived for nine months, then died a crib death. At autopsy, an enlarged, but structurally normal, thymus was found. Light microscopically, the epidermis showed massive hyperkeratosis and variable parakeratosis, and a stain for neutral fat was positive in the upper epidermis and stratum corneum. Electron microscopic study disclosed crystals resembling cholesterol and masses of autophagic vacuoles, many of them glutted with lipid, deposited within cells of the stratum corneum. Biochemically, cholesterol and triglyceride levels in the stratum corneum were sharply elevated (19.8 and 32.0 mg/g of dry weight, respectively). A defect in epidermal lipid metabolism is postulated.     

Alpha hydroxy acids: procedures for use in clinical practice

Alpha hydroxy acids and alpha keto acids applied topically in lower concentrations reduce the thickness of hyperkeratotic stratum corneum by reducing corneocyte cohesion at lower levels of the stratum corneum. This property permits efficient clinical control of dry skin, ichthyosis, follicular hyperkeratosis, and other conditions characterized by retention of stratum corneum. Applied topically in higher concentrations, these acids cause epidermolysis. This property provides a new alternative for treating seborrheic keratoses, keratoses commonly known as "age spots," actinic keratoses, and verrucae vulgares; all of which lesions involve distinct epidermal hyperplasia as well as retention of stratum corneum. Facial wrinkles can be modified with topical alpha hydroxy acids, applied in higher concentrations as office procedures, and concomitant daily home application of lower concentrations.     

The ‘dry’ non-eczematous skin associated with atopic eczema*

The non-eczematous but ‘dry’ skin of twelve patients with eczema has been studied and contrasted with skin from similar sites in control subjects of similar age and sex and with patients with autosomal dominant ichthyosis. The areas investigated were examined histologically and by techniques for assessment of the stratum corneum structure and function. The ‘dry’ skin sites demonstrated increased intracorneal cohesion, increased total epidermal thickness, patchy parakeratosis and in places slight hypergranulosis. It is concluded that the dry skin condition of patients with atopic eczema is not autosomal dominant ichthyosis and is probably eczematous in nature.     

Ichthyosis in Sjögren–Larsson syndrome reflects defective barrier function due to abnormal lamellar body structure and secretion

Sjögren–Larsson syndrome is a genetic disease characterized by ichthyosis, mental retardation, spasticity and mutations in the ALDH3A2 gene coding for fatty aldehyde dehydrogenase, an enzyme necessary for oxidation of fatty aldehydes and fatty alcohols. We investigated the cutaneous abnormalities in 9 patients with Sjögren–Larsson syndrome to better understand how the enzymatic deficiency results in epidermal dysfunction. Histochemical staining for aldehyde oxidizing activity was profoundly reduced in the epidermis. Colloidal lanthanum perfusion studies showed abnormal movement of tracer into the extracellular spaces of the stratum corneum consistent with a leaky water barrier. The barrier defect could be attributed to the presence of abnormal lamellar bodies, many with disrupted limiting membranes or lacking lamellar contents. Entombed lamellar bodies were present in the cytoplasm of corneocytes suggesting blockade of lamellar body secretion. At the stratum granulosum–stratum corneum interface, non-lamellar material displaced or replaced secreted lamellar membranes, and in the stratum corneum, the number of lamellar bilayers declined and lamellar membrane organization was disrupted by foci of lamellar/non-lamellar phase separation. These studies demonstrate the presence of a permeability barrier abnormality in Sjögren–Larsson syndrome, which localizes to the stratum corneum interstices and can be attributed to abnormalities in lamellar body formation and secretion.     

Autosomal-dominant lamellar ichthyosis: Ultrastructural characteristics of a new type of congenital ichthyosis

Summary Recently, autosomal-dominant lamellar ichthyosis (ADLI) has been shown to be a new genetic trait with clinical and histologic features similar to those of autosomal-recessive lamellar ichthyosis. In two patients affected with ADLI, the malpighian keratinocytes showed ultrastructural signs of increased cellular metabolism. The tonofilaments and keratohyaline granules were regular in structure and number. However, as a distinctive ultrastructural feature, a prominent transforming zone was found between the granular and horny layers. Moreover, a normal keratin pattern and only a limited number of lipid inclusions were observed in the stratum corneum. Thus, ADLI can be distinguished from the autosomal-recessive forms of lamellar ichthyosis, permitting a correct diagnosis when genetic counselling has to be given in sporadic cases.     

Exogenous origin of n-alkanes in pathologic scale.

BACKGROUND--Although n-alkanes accumulate in some disorders of cornification, recent studies using radioactive carbon 14 content by accelerator mass spectrometry point to an exogenous origin for alkanes in normal stratum corneum, and their derivation in congenital ichthyosiform erythroderma remains controversial. DESIGN AND RESULTS--Using 14C content to measure sample age, the n-alkane fractions from two patients with congenital ichthyosiform erythroderma contained no detectable contemporary materials. By electron microscopy, alkane-enriched emollients (petrolatum [Vaseline]) permeated to all levels of stratum corneum of hairless mice, expanding the intercellular domains and distorting membrane bilayers. Similar ultrastructural changes were also observed in the stratum corneum of patients with congenital ichthyosiform erythroderma. When alkanes were excluded, no differences in lipid content were evident between two forms of autosomal recessive ichthyosis. CONCLUSIONS--These data demonstrate that scale n-alkanes in disorders of cornification derive from environmental sources and indicate the pervasiveness of petroleum-based emollients in skin. Therefore, epidermal lipid analyses must be interpreted with caution. However, these studies do not rule out an important therapeutic and/or pathogenic role for exogenous n-alkanes in skin.     

Harlequin ichthyosis and other autosomal recessive congenital ichthyoses: the underlying genetic defects and pathomechanisms

Autosomal recessive congenital ichthyoses (ARCI) include several severe subtypes including harlequin ichthyosis (HI), lamellar ichthyosis and non-bullous congenital ichthyosiform erythroderma. Patients with these severe types of ichthyoses frequently show severe hyperkeratosis and scales over a large part of the body surface form birth and their quality of life is often severely affected. Recently, research into the pathomechanisms of these severe congenital ichthyoses have advanced dramatically and led to the identification of several causative genes and molecules underlying the genetic defects. To date, seven loci have been identified that are associated with ARCI and, among them, five causative genes and molecules have been detected. The five genes are transglutaminase 1 gene (TGM1), ABCA12, two lipoxygenase genes, ALOXE3 and ALOX12B and ichthyin. One of these components, ABCA12, has recently been shown to be a keratinocyte lipid transporter associated with lipid transport in lamellar granules and loss of ABCA12 function leads to a defective lipid barrier in the stratum corneum, resulting in the HI phenotype. Transglutaminse 1 deficiency was reported to cause a malformed cornified cell envelope leading to a defect in the intercellular lipid layers in the stratum corneum and defective stratum corneum barrier function resulting in an ichthyosis phenotype. Thus, defective intercellular lipid layers are major findings in autosomal recessive congenital ichthyoses. Information concerning ARCI genetic defects and disease pathomechanisms are beneficial for providing better treatments and genetic counseling including prenatal diagnosis for families affect by ichthyoses.     

Congenital ichthyosis: an overview of current and emerging therapies

Congenital ichthyosis is a collective name for a group of monogenetic disorders of cornification, sometimes associated with systemic symptoms. There may be an abnormal quality or quantity of scale produced, abnormal thickness of stratum corneum or abnormal keratinocyte kinetics, often associated with skin inflammation. Pruritus, skin fragility, ectropion and anhidrosis are sometimes associated with the rare types of ichthyosis. Three important mechanisms are involved in the action of topical agents used in the treatment of ichthyosis: hydration, lubrication and keratolysis. The latter effect can also be achieved with systemic retinoids. For ichthyosis with an increased tendency towards skin infections, antimicrobials are another group of widely used agents. Considering that patients with ichthyosis are potential mega-users of topical therapy, with an estimated lifetime consumption of approximately one tonne cream per capita, surprisingly few controlled trials of the various treatments have been performed. Moreover, nearly all therapeutic principles were established long before the recent increase in knowledge about the aetiology and pathophysiology of ichthyosis. This calls for new ideas and intensified efforts to develop future ichthyosis therapies.     

Expression of stratum corneum chymotryptic enzyme in ichthyoses and squamoproliferative processes

OBJECTIVE: Stratum corneum chymotryptic enzyme (SCCE) is a serine protease, which is thought to play a role in the desquamation of skin via the proteolysis of desmosomes in the stratum corneum. The objective of this study was to investigate the expression of SCCE in ichthyoses and squamoproliferative processes, conditions in which the shedding and replacement of epidermal cells is disrupted. DESIGN: Tissue samples from cases of Netherton's syndrome, congenital ichthyosiform erythroderma, ichthyosis vulgaris, actinic keratosis, squamous cell carcinoma in situ, and invasive squamous cell carcinoma were examined for expression of SCCE using immunohistochemistry. MAIN OUTCOME MEASURES: The slides were qualitatively analyzed for the expression of SCCE by a certified dermatopathologist. RESULTS: In all disease states, we found that the expression of SCCE was absent in areas of parakeratotic stratum corneum of normal thickness. In areas of mixed orthokeratosis and parakeratosis where the stratum corneum was greatly thickened as might correspond clinically to a cutaneous horn, SCCE staining was either absent or focally aggregated without regard to orthokeratosis or parakeratosis. Of note, complete absence of SCCE expression was not observed in any of the cases of ichthyosis examined, nor was there increased expression of SCCE in the atypical cells of the squamoproliferative disorders. CONCLUSIONS: These results suggest that SCCE is abnormally expressed in skin where epidermal cell kinetics are disrupted due to inherited and acquired defects. Further investigation is needed to determine causality between the abnormal expression of SCCE and the altered cell kinetics in these diseases.     

表皮松解角化过度性鱼鳞病1例

患者男,23岁,全身皮肤潮红、粗糙、水疱和脱屑23年。皮损组织病理示:表皮角化过度,颗粒层增厚,颗粒层细胞内含大量透明角质颗粒,细胞核皱缩,核周空泡化,细胞边界不清,形态不规则,呈表皮松解性角化过度改变。诊断:表皮松解角化过度性鱼鳞病。     

Ichthyosis vulgaris: identification of a defect in synthesis of filaggrin correlated with an absence of keratohyaline granules

Ichthyosis vulgaris is an autosomal dominant disorder of keratinization characterized histologically by absent or reduced keratohyaline granules in the epidermis and mild hyperkeratosis. The basic defect in ichthyosis vulgaris is unknown. We have tested for the presence of filaggrin and its precursor, profilaggrin, in the epidermis of affected and unaffected individuals from 2 families with ichthyosis vulgaris and correlated its presence and relative quantity with ultrastructure findings in the same individuals. Filaggrin was present on stained sodium dodecyl sulfate gels and immunoblots of epidermal proteins from controls and unaffected family members. It was absent from the more severely affected individuals in each family and reduced in intensity in the less severely affected family members. Immunohistology in controls showed localization of filaggrin-related protein in the stratum corneum and within the granular layer. In contrast, tissue from affected individuals showed little or no reaction. Electron microscopic studies showed that keratohyaline granules were absent in 3 severely affected individuals, and reduced in number in the others. The relative amount of keratohyalin by electron microscopy correlated with the amount of filaggrin detectable on immunoblots. The stratum corneum was thicker than in normals but showed the typical "keratin pattern" staining suggesting that filaggrin is not essential for keratin filament aggregation and may have another function in vivo. We have demonstrated that the structural proteins, profilaggrin and filaggrin, are reduced or absent in 5 patients from 2 pedigrees with ichthyosis vulgaris. This biochemical abnormality correlates with the morphologic reduction in the amount of keratohyalin, and with the clinical severity of the disorder.     

Neutral lipid storage disease with ichthyosis. Defective lamellar body contents and intracellular dispersion

Although the link between epidermal lamellar body lipids and stratum corneum barrier function is well established, a role for lamellar body lipids in desquamation remains unproved. We examined skin biopsy material from three family members of a Palestinian kindred with a multisystem disorder of altered lipid metabolism, ichthyosis, and deposition of fat droplets in multiple tissues (Chanarin-Dorfman syndrome, neutral lipid storage disease). Thin-section and freeze-fracture ultrastructural studies revealed a distinctive lamellar body abnormality: multilaminated spherules that distorted and displaced the normal internal disk structure of these organelles. Whereas these spherules remained interspersed with secreted lamellar body contents within the intercellular spaces of the outer epidermis, at the stratum granulosum-stratum corneum interface they apparently dispersed into electron-lucent "slits." These studies therefore provide strong support for the concept that lamellar body-derived lipids influence stratum corneum desquamation and further suggest that abnormalities of neutral lipid-alkane metabolism influence normal epidermal shedding.