Clinical and biochemical footprints of inherited metabolic diseases. VI. Metabolic dermatoses

Cutaneous signs and symptoms may facilitate the diagnosis or can help in identifying complications or side effects of overtreatment of inherited metabolic diseases. The principal manifestations can be grouped into vascular lesions, ichthyosis, papular and nodular skin lesions, abnormal pigmentation, photosensitivity, skin laxity, hair shaft involvement, and nail abnormalities. We have summarized associations of these cutaneous signs and symptoms in 252 inherited metabolic diseases. This represents the sixth of a series of articles attempting to create and maintain a comprehensive list of clinical and metabolic differential diagnoses according to system involvement.

Molecular Genetics of Keratinization Disorders - What's New About Ichthyosis

The heritable forms of keratinization disorders, including various forms of ichthyosis and keratodermas, comprise a phenotypically heterogeneous group of diseases which can be divided into syndromic and non-syndromic forms. In the non-syndromic forms, the clinical manifestations are limited to the cutaneous structures while the syndromic ones are associated with a spectrum of extracutaneous manifestations. The inheritance in different families can be autosomal dominant, autosomal recessive or either X-linked dominant or recessive. Currently at least 67 distinct genes have been associated with different forms of ichthyosis. These genes can be grouped on the basis of their physiological involvement, including genes encoding structural components of epidermis, those involved in epidermal lipid metabolism, or those critical for cell-cell adhesion, and keratinocyte differentiation. This overview highlights some of the recent progress made in understanding the molecular genetics of keratinization disorders, and presents selected, recently characterized cases as representative of different forms of heritable ichthyosis.

Genetics of Inherited Ichthyoses and Related Diseases

Inherited ichthyoses are classified as Mendelian disorders of cornification (MEDOC), which are defined on the basis of clinical and genetic features and are mainly divided into non-syndromic and syndromic ichthyoses. Numerous genes, which encode for corresponding proteins, are involved in the normal differentiation of keratinocytes (cornification) and participate in the formation of a functional epidermal barrier. To date, mutations in more than 50 genes are known to result in various types of ichthyoses. Thanks to modern genetic diagnostic methods based on targeted next generation sequencing (NGS), approximately 80-90% of cases can be resolved at present. Further sequencing methods covering the whole exome (WES) or whole genome (WGS) will obviously elucidate another portion of the remaining unknown ichthyoses in the future.

Ichthyosis: A Road Model for Skin Research

The understanding of monogenetic disorders of cornification, including the group of diseases called ichthyoses, has expanded greatly in recent years. Studies of the aetiology of more than 50 types of ichthyosis have almost invariably uncovered errors in the biosynthesis of epidermal lipids or structural proteins essential for normal skin barrier function. The barrier abnormality per se may elicit epidermal inflammation, hyperproliferation and hyperkeratosis, potentially contributing to the patient's skin symptoms. Despite this and other new knowledge about pathomechanisms, treatment of ichthyosis often remains unsatisfactory. This review highlights a series of approaches used to elucidate the pathobiology and clinical consequences of different types of ichthyosis, and related diseases with the ultimate goal of finding new and better treatments.

Biotinidase deficiency in a newborn

INTRODUCTION

Biotinidase deficiency is an inherited disorder of biotin metabolism that is untreated may present within the first few month of life.

OBJECTIVE

We report the exceptional observation of a biotinidase deficiency in Morocco. The rarity of this pathology, its age of onset, its mode of revelation and the lack of treatment in Morocco make the particularity of this observation.

OBSERVATION

A newborn child born from a 24-year-old mother, followed by an estimated pregnancy of 37 weeks of amenorrhea according to the Farr score (morphological maturation score used for the dating of the pregnancy term). The infant presented at 7 days of life with a cutaneous-mucous eruption with icithiosic dry erythroderma of interest to the trunk, the face, the scalp associated with alopecia and depilation of the eyebrow. The biotinoidase deficiency was confirmed by its low serum concentration at 49 nka / l. The newborn died at 20 days of life before starting the specific treatment.

CONCLUSION

Biotinidase deficiency is a rare condition requiring early screening and rapid management. The delay in diagnosis and the unavailability of treatment in Morocco can have fatal consequences.

Management of Ichthyosis: A Brief Review

The ichthyoses, also termed the disorders of keratinization, are a heterogenous group of skin diseases in which a distinctive horny layer arises secondary to excessive transepidermal water loss. Although occasionally acquired, the majority of ichthyoses are inherited and can be pinpointed to characteristic genetic mutations. Management depends on disease severity and includes topical agents and lifestyle modifications with or without oral retinoids. Genetic counseling is also an important consideration. This review aims to highlight advances in our understanding of disease pathogenesis as well as the holistic approach necessary to adequately manage ichthyosis patients.

Standards for the Protection of Skin Barrier Function

The skin is a vital organ, and through our skin we are in close contact with the entire environment. If we lose our skin we lose our life. The barrier function of the skin is mainly driven by the sophisticated epidermis in close relationship with the dermis. The epidermal epithelium is a mechanically, chemically, biologically and immunologically active barrier submitted to continuous turnover. The barrier function of the skin needs to be protected and restored. Its own physiology allows its recovery, but many times this is not sufficient. This chapter is focused on the standards to restore, treat and prevent barrier function disruption. These standards were developed from a scientific, academic and clinical point of view. There is a lack of standardized administrative recommendations. Still, there is a walk to do that will help to reduce the social and economic burden of diseases characterized by an abnormal skin barrier function.

[Epidermal barrier - molecular structure and disorders in selected ichthyoses]

Ichthyosis is a rare, clinically heterogeneous group of 36 skin diseases with Mendelian inheritance, characterized by disorders of cornification (MeDOC, Mendelian Disorders Of Cornification). Currently there are 35 genes known which mutations are a molecular cause of different MeDOC. They encode proteins involved in the processes of keratinocytes differentiation, lipid synthesis and metabolism and DNA repair. Despite of this high molecular heterogeneity that leads to dysfunction and structure disorder of various epidermal components, the secondary effect of mutations in different genes is similar - disruption of the epidermal barrier and elevated transepidermal water loss. Disturbances in this basic epidermal protective function activate the repair mechanisms within the epidermis and lead i.a. to the primary symptom of MeDOC - hyperkeratosis. In this review we presented the current knowledge of biochemical processes and molecular causes of clinical symptoms based on selected examples of MeDOC.

Nalfurafine suppresses pruritogen- and touch-evoked scratching behavior in models of acute and chronic itch in mice

The kappa-opioid agonist, nalfurafine, has been approved in Japan for treatment of itch in patients with chronic kidney disease. We presently investigated if systemic administration of nalfurafine inhibited ongoing or touch-evoked scratching behavior (alloknesis) following acute intradermal injection of histamine or the non-histaminergic itch mediator, chloroquine, in mice. We also investigated if nalfurafine suppressed spontaneous or touch-evoked scratching in an experimental model of chronic dry skin itch. Nalfurafine reduced scratching evoked by histamine and chloroquine. Following acute histamine, but not chloroquine, low-threshold mechanical stimuli reliably elicited directed hindlimb scratching behavior, which was significantly attenuated by nalfurafine. In mice with experimental dry skin, nalfurafine abolished spontaneous scratching but had no effect on alloknesis. Nalfurafine thus appears to be a promising treatment for acute itch as well as ongoing itch of dry skin.

Pruritic eruption on the chest

The fact that this patient's rash was limited to his chest provided an important diagnostic clue.

Inherited ichthyoses/generalized Mendelian disorders of cornification

Inherited ichthyoses, defined as the generalized form of Mendelian disorders of cornification, are characterized by visible scaling and/or hyperkeratosis of most or all of the skin. This etiologically and phenotypically heterogenous group of conditions is caused by mutations in various different genes important for keratinocyte differentiation and epidermal barrier function. Diagnosing a specific entity is a particular challenge for the nonspecialist presented with the common clinical scaling. For the clinician, this review outlines an algorithmic approach for utilizing diagnostic clues to narrow down the differential diagnosis and to guide further testing and treatment options.

Interactions between FATP4 and ichthyin in epidermal lipid processing may provide clues to the pathogenesis of autosomal recessive congenital ichthyosis

BACKGROUND

Autosomal recessive congenital ichthyosis (ARCI) is caused by mutations in ≥10 different genes, of which transglutaminase-1 (TGM1) predominates. A rare form is ichthyosis prematurity syndrome (IPS) caused by mutations in SLC27A4 encoding fatty acid transporter protein 4 (FATP4), believed to be an acyl-CoA synthetase activating long- and very-long-chain FA. Another ARCI is caused by mutations in NIPAL4, coding for ichthyin, which is proposed to be a magnesium transporter or a trans-membrane receptor. A possible interaction between FATP4 and ichthyin has not been studied before.

OBJECTIVE

To find common denominators in the pathogenesis of ARCI.

METHODS

FATP4 and ichthyin were analyzed by immunofluorescence and proximity ligation assay (PLA) in healthy and ARCI patient skin and in in vitro models of ARCI epidermis.

RESULTS

Both proteins were expressed in the upper stratum granulosum of normal epidermis and PLA confirmed a close interaction between FATP4 and ichthyin. In IPS skin lacking FATP4 we found reduced ichthyin expression and this finding could be reproduced in organotypic epidermis with siRNA silenced SLC27A4. In contrast, increased FATP4 staining was found in patients with ichthyin (NIPAL4) mutations and in organotypic epidermis with silenced NIPAL4. In patients with TGM1 mutations, the expression of both FATP4 and ichthyin was increased, but the PLA signal was low probably indicating a malfunctioning protein interaction.

CONCLUSION

Our study suggests that FATP4, ichthyin and TGM1 interact in lipid processing essential for maintaining the epidermal barrier function. It is also hypothesized that ichthyin serves as Mg(2+)-transporter for FATP4 in this process.

[Diagnostics of keratitis-ichthyosis-deafness syndrome (KID- syndrome)]

The combination of pre-lingual and sensorinerual deafness with skin hyperkeratinization is a relatively rare pathology. Only 11 families affected by this disorder were described in the literature during the last 30 years (from 1975 to 2002). To date, there are no more than 50 cases of this condition known in the world. Modern molecular methods revealed in all such patients a mutation in the GJB2 gene as the primary cause of the disease. We studied a 4 year-old girl with bilateral congenital grade IV sensorineural deafness. Her unusual appearance drew attention aas early as the primary examination; the patient had the deep-set eyes and dry skin over the entire body, she presented with hypotrichosis of the scalp, thin and light-blond hair. Analysis of the nucleotide sequence of the GJB2 gene revealed the substitution of guanine-148 by adenine that led to D50N amino acid substitution. This dominant mutation proved to be the cause of keratitis-ichthyosis-deafness syndrome (KID-syndrome). A review of the literature concerning molecular diagnostics and clinical features of this syndrome is presented. The results of molecular-genetic investigations provided the data on pathogenesis of different variants of sensorineural deafness and the associated genotype-phenotype relationships that may be used as a basis for the further development of the methods for the prevention and treatment of KID-syndrome.

Ichthyosis: clinical manifestations and practical treatment options

Ichthyoses constitute a large group of cornification disorders that affect the entire integument. The skin is characterized by visible scaling and in many cases by inflammation, for example, in bullous/keratinopathic ichthyosis or Netherton syndrome. From the viewpoint of classification it is useful to distinguish non-syndromic from syndromic types of ichthyosis. Ichthyosis vulgaris and recessive X-linked ichthyosis are common disorders - often of delayed onset, in contrast to congenital ichthyoses, which belong to the group of rare diseases and present at birth with either the features of collodion membrane or congenital ichthyosiform erythroderma. The diagnostic steps are based on clinical data, analyses such as the steroid sulfatase activity test, skin biopsies, and genetic results. However, the dramatic increase in knowledge about the pathophysiology of these conditions has not led to a curative therapy so far. The therapeutic management is multidisciplinary and involves ichthyosis patient organizations in many countries. The mainstay of treatment remains with moisturizing creams containing, for example, urea, lactic acid and other humectants and keratolytics, regular bathing, and mechanical scale removal. Patients with lamellar ichthyosis or ichthyosiform erythroderma in particular profit from oral therapy with retinoids or retinoic acid metabolism-blocking agents.

Management of dry skin conditions in older people

This article examines the physiological changes that occur in the skin with advancing age that make it more prone to skin problems. Examples of common skin disorders that may affect older people are provided. Intrinsic factors such as a genetic tendency to eczema, and extrinsic factors such as the effects of sun damage and general poor health can both affect the skin of older people. The management of dry skin conditions in this age group is investigated and the value of emollient therapy, involving the use of bath emollients, soap substitutes and leave-on emollient lotions, creams or ointments, is discussed.

Aberrant hemichannel properties of Cx26 mutations causing skin disease and deafness

Mutations in the human GJB2 gene, which encodes connexin26 (Cx26), underlie various forms of hereditary deafness and skin disease. While it has proven difficult to discern the exact pathological mechanisms that cause these disorders, studies have shown that the loss or abnormal function of Cx26 protein has a profound effect on tissue homeostasis. Here, we used the Xenopus oocyte expression system to examine the functional characteristics of a Cx26 mutation (G45E) that results in keratitis-ichthyosis-deafness syndrome (KIDS) with a fatal outcome. Our data showed that oocytes were able to express both wild-type Cx26 and its G45E variant, each of which formed hemichannels and gap junction channels. However, Cx26-G45E hemichannels displayed significantly greater whole cell currents than wild-type Cx26, leading to cell lysis and death. This severe phenotype could be rescued in the presence of elevated Ca(2+) levels in the extracellular milieu. Cx26-G45E could also form intercellular channels with a similar efficiency as wild-type Cx26, however, with increased voltage sensitive gating. We also compared Cx26-G45E with a previously described Cx26 mutant, A40V, which has an overlapping human phenotype. We found that both dominant Cx26 mutants elicited similar functional consequences and that cells coexpressing mutant and wild-type connexins predominantly displayed mutant-like behavior. These data suggest that mutant hemichannels may act on cellular homeostasis in a manner that can be detrimental to the tissues in which they are expressed.

Drosophila spichthyin inhibits BMP signaling and regulates synaptic growth and axonal microtubules

To understand the functions of NIPA1, mutated in the neurodegenerative disease hereditary spastic paraplegia, and of ichthyin, mutated in autosomal recessive congenital ichthyosis, we have studied their Drosophila melanogaster ortholog, spichthyin (Spict). Spict is found on early endosomes. Loss of Spict leads to upregulation of bone morphogenetic protein (BMP) signaling and expansion of the neuromuscular junction. BMP signaling is also necessary for a normal microtubule cytoskeleton and axonal transport; analysis of loss- and gain-of-function phenotypes indicate that Spict may antagonize this function of BMP signaling. Spict interacts with BMP receptors and promotes their internalization from the plasma membrane, implying that it inhibits BMP signaling by regulating BMP receptor traffic. This is the first demonstration of a role for a hereditary spastic paraplegia protein or ichthyin family member in a specific signaling pathway, and implies disease mechanisms for hereditary spastic paraplegia that involve dependence of the microtubule cytoskeleton on BMP signaling.

Role of epidermis-type lipoxygenases for skin barrier function and adipocyte differentiation

12R-lipoxygenase (12R-LOX) and epidermis-type LOX-3 (eLOX-3) are novel members of the multigene family of mammalian LOX. A considerable gap exists between the identification of these enzymes and their biologic function. Here, we present evidence that 12R-LOX and eLOX-3, acting in sequence, and eLOX-3 in combination with another, not yet identified LOX are critically involved in terminal differentiation of keratinocytes and adipocytes, respectively. Mutational inactivation of 12R-LOX and/or eLOX-3 has been found to be associated with development of an inherited ichthyosiform skin disorder in humans and genetic ablation of 12R-LOX causes a severe impairment of the epidermal lipid barrier in mice leading to post-natal death of the animals. In preadipocytes, a LOX-dependent PPARgamma activating ligand is released into the cell supernatant early upon induction of differentiation and available evidence indicates that this ligand is an eLOX-3-derived product. In accordance with this data is the observation that forced expression of eLOX-3 enhances adipocyte differentiation.

Proton magnetic resonance spectroscopy findings and clinical effects of montelukast sodium in a case with Sjögren-Larsson syndrome

Sjögren-Larsson syndrome is a rare hereditary metabolic disorder characterized by congenital ichthyosis, mental retardation, and spastic diplegia or tetraplegia. This genetic disease is caused by fatty acid aldehyde dehydrogenase deficiency, leading to an accumulation of long-chain alcohols. The role of enzyme in the degradation of leukotrienes paved the way to the development of a new therapeutic strategy for Sjögren-Larsson syndrome, leukotriene antagonists. We describe a 3-year-old boy with Sjögren-Larsson syndrome who had a lipid peak on proton magnetic resonance spectroscopy despite normal findings on cerebral magnetic resonance imaging. He benefited from treatment with montelukast sodium, especially with respect to the agonizing pruritus.

Atopic xerosis: employment of noninvasive biophysical instrumentation for the functional analyses of the mildly abnormal stratum corneum and for the efficacy assessment of skin care products

The subtle dryness of the skin surrounding the lesions of atopic dermatitis (AD) is called atopic dry skin or atopic xerosis (AX). AX is more susceptible to the development of AD skin lesions under various environmental stimuli than the clinically normal skin of the people who have or have had or will have AD, which might be called normal atopic skin (NAS) that shows no functional differences as compared to the skin of normal individuals. Routine histopathologic studies of AX that involve the invasive procedures of biopsy are not so helpful in clarifying the underlying pathogenesis. Modern, noninvasive biophysical instrumentation provides rich and quantitative information about various functional aspects of skin. The stratum corneum (SC) of AX reveals not only decreased hydration but also mildly impaired barrier function demonstrable as an increase in transepidermal water loss, elevated pH values, and an increased turnover rate of the SC consisting of thick layers of smaller-sized corneocytes. These data suggest that AX is related to mildly increased epidermal proliferation as a result of the presence of subclinical cutaneous inflammation. Although AX skin does not display any impairment in the recovery of barrier function after physical skin irritation by tape-stripping, it produces a much more severe, long-lasting inflammatory response together with a delay in barrier repair after chemical irritation such as that induced by sodium lauryl sulphate. The SC of AX is biochemically characterized by reduction in the amounts of ceramides, especially ceramide I, sebum lipids, and water-soluble amino acids. None of these changes in SC functions are seen in NAS, which includes not only the normal-looking skin of AD patients long after regression of all active lesions but also of latent atopic skin such as neonates who later develop AD. This suggests that all of the observed functional as well as biochemical abnormalities of AX are a reflection of subclinical inflammation. The presence of the underlying inflammation in AX also differentiates it from senile xerosis. The mildly impaired SC functions of AX can be improved by daily repeated applications of effective moisturizers, i.e., corneotherapy, which is effective in preventing the exacerbating progression of AX to AD resulting from inadvertent scratching of the skin that facilitates the penetration of environmental allergens into the skin. The biophysical confirmation of such efficacy of moisturizers, including cosmetic bases on the mildly impaired barrier function and decreased water-holding capacity of the SC of AX, definitely substantiates the importance of skin care for the cosmetic skin problems that affect every individual in the cold and dry season ranging from late autumn to early spring.

Neurotological and neuroanatomical changes in the connexin-26-related HID/KID syndrome

The phenotype of the HID (hystrix-like ichthyosis, deafness)/KID (keratitis, ichthyosis, deafness) syndrome is primarily characterized by skin changes. However, the connexin 26 (Cx 26) autosomal dominant mutation underlying this syndrome is of special neurotological interest. In the present paper, the clinical pattern, audiovestibular and neuroimaging findings and the detailed genetic analysis of 4 patients with identical HID/KID-associated mutation D50N of Cx 26 are reported. The audiological test results demonstrated profound sensorineural hearing loss in all of the patients. Neurotological testing revealed inconsistent abnormalities in dynamic posturography (sensory organization test), but the vestibular ocular reflex upon caloric irrigation was normal in all patients. Vestibular-evoked myogenic potential testing for otolith function (saccule) showed a regular response in 1 patient and pathologic responses in 3 patients, while subjective haptic vertical (utricular function) testing was normal in all of the patients. CCT showed an extended (in length), but very thin (in diameter) bony lining between the basal portion of the internal auditory canal and the vestibule in the 3 scanned patients. Our study provides evidence for functionally intact semicircular canals and normal utricular function in subjects with the autosomal dominant D50N mutation of Cx 26, in contrast to saccular function which was generally compromised and hearing loss which was profound.

[Diverse mechanisms of itch]

Itch is known to be a sensation that provokes a desire to scratch. It is a bio-warning sensation, which serves to detect and remove parasites and irritants in the superficial layers of the skin and the mucous membrane. The mechanisms of itch are not simple. It is mediated by mast cells and keratinocytes, which each produce and release a few itch mediators. Alterations in the distribution of primary afferent fibers in the epidermis are also involved in itch. Agents that have a wide spectrum of inhibitory action on mast cells, keratinocytes and primary afferents may be needed to effectively suppress itch.

[The so-called dry skin of the diabetic patient]

Rough skin or xerosis, known by the laity as dry skin, results from a defect in the stratum corneum desquamation which normally remains imperceptible. This condition is negatively influenced by winter climatic conditions. Atopic dermatitis and trophic changes related to post-menopause, ageing, diabetes mellitus, as well as other endrocrine and metabolic disturbances are also involved in this process. Xerosis can be improved at various degrees by emollients, humectants, hydrating agents and squamolytic agents.

Pathophysiologic basis for growth failure in children with ichthyosis: an evaluation of cutaneous ultrastructure, epidermal permeability barrier function, and energy expenditure

OBJECTIVE

Because an impaired epidermal permeability barrier is present in many of the ichthyoses, we examined the contribution of barrier failure to caloric requirements in children with ichthyosis and growth failure.

STUDY DESIGN

Transepidermal water loss (TEWL) and ultrastructural parameters of the permeability barrier were evaluated in 10 hospitalized children with ichthyosis and growth failure. Nutritional intake, resting energy expenditure, and calories lost as heat of evaporation were determined.

RESULTS

Mean basal TEWL rates were markedly elevated in all study patients in comparison to the expected upper limit of normal (39.6+/-20.6 vs 8.7 mL/m(2) per hour). The severity of abnormalities in the ultrastructure of permeability barrier-related structures, assessed semiquantitatively, correlated significantly to mean basal TEWL rates (P <.001). Total body daily TEWL was elevated (746 +/- 468 vs 209 mL/d), resulting in a caloric drain of 433 +/- 272 kcal/d (21 +/- 9.8 kcal/kg per day) through heat of evaporation. Nutrient intake exceeded requirements in all, but resting energy expenditure exceeded predicted in 5 of 6 patients and correlated significantly with mean basal TEWL rates (P <.005).

CONCLUSIONS

A defective permeability barrier in children with ichthyosis can result in ample chronic losses of water and calories to impair growth.

Nutritional status and gastrointestinal structure and function in children with ichthyosis and growth failure

Growth failure occurs in several of the ichthyoses, a heterogeneous group of inherited disorders characterized by thickened or scaly skin. This suggests that there may be common pathogenic mechanisms causing failure to thrive. Previous studies have proposed that a hypermetabolic state induced by epidermal inflammation and hyperproliferation or enteropathy leading to malabsorption and nutritional deficiencies might account for the growth failure in icthyosis.

OBJECTIVE

The purpose of this study was to examine the extent of enteropathy and nutritional deficiency in children with severe ichthyosis and growth failure.

METHODS

Ten children with different types of ichthyoses and growth failure were studied.

RESULTS

Evaluation of gastrointestinal structure and function revealed few abnormalities other than mild fat malabsorption in two patients. Total caloric intake exceeded established requirements for age, height, and weight in all patients. Deficiencies of fat-soluble vitamins were identified in a few subjects. Mild elevations in total calcium and magnesium blood level, elevated hematocrit levels, and constipation were observed in many patients.

CONCLUSIONS

Nutritional deficiencies and gastrointestinal abnormalities are uncommon in children with ichthyosis and failure to thrive. Chronic hypovolemia caused by impaired epidermal permeability barrier may be common in this population.

Conséquences fonctionnelles des perturbations des lipides cutanés

Epidermal lipids constitute an ultimate frontier between the organism and its environment. Their essential role consists of providing a barrier limiting both transepidermal water loss and penetration of external factors, such as irritants. Efficacy of the barrier depends on the physicochemical properties of the substance applied to the skin surface and the increase in transepidermal water loss, which may be quantified, is proportional to the provoked perturbation in the barrier function. In atopic dermatitis epidermis, a significant decrease in the ceramide content and abnormally low levels of omega-6 fatty acids correlate with an increased rate of water loss at the skin surface--a sign of an impaired barrier. However, similar signs are observed in the atrophic epidermis provoked by long term local corticotherapy. Epidermal lipid profiles are also seriously modified in various ichthyoses, and are partially responsible for the hyperkeratosis observed clinically, e.g.: the recessive X-linked form is provoked by a mutation of the steroid sulphatase gene and the resulting accumulation of unconverted precursor of cholesterol. Modification of the lipid composition in acne contributes to comedo formation, whereas UV improves barrier function (and may provoke hyperkeratosis) through an increase in the stratum corneum lipid content. Another source of lipids at the epidermal surface is sebaceous glands. Waxes present in the sebum increase friction coefficient of the skin surface. Sebum also influences (decreases) the rate of penetration of lipophilic substances applied on the skin. Its role in the skin biology appears to be less vital than that of the lipids constituting the permeability barrier of the stratum corneum.

The development and initial validation of the Liverpool sicca index to assess symptoms and dysfunction in patients with primary Sjögren's syndrome

BACKGROUND

A validated measure to assess sicca-related symptoms in patients with primary Sjögren's syndrome (1 degrees SS) is required for clinical studies.

METHODS

A self-administered questionnaire was developed to assess sicca-related symptoms and dysfunction in 1 degrees SS. This was administered to three groups of 40 respondents to measure construct validity: 1 degrees SS patients, non-SS patients reporting xerostomia and a non-patient group. The frequency of scores and the mean score for each question were calculated for each group. Reliability was assessed by test/retest.

RESULTS

The measure consisted of 28 items divided into five domains. Scores for questions in domains were generally worse (higher) for 1 degrees SS patients than for patients with xerostomia. The non-patient group reported the best (lowest) scores for all questions. The Kappa statistic for all but four questions was greater than 0.6, suggesting good reliability.

CONCLUSION

Questionnaire showed good construct validity and reliability. The Liverpool sicca index needs to be further validated in larger, multicentre studies.

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.

Transglutaminases in disease

Transglutaminases (TGases) are enzymes that are widely used in many biological systems for generic tissue stabilization purposes. Mutations resulting in lost activity underlie several serious disorders. In addition, new evidence documents that they may also be aberrantly activated in tissues and cells and contribute to a variety of diseases, including neurodegenerative diseases such as Alzheimer's and Huntington's diseases. In these cases, the TGases appear to be a factor in the formation of inappropriate proteinaceous aggregates that may be cytotoxic. In other cases such as celiac disease, however, TGases are involved in the generation of autoantibodies. Further, in diseases such as progressive supranuclear palsy, Huntington's, Alzheimer's and Parkinson's diseases, the aberrant activation of TGases may be caused by oxidative stress and inflammation. This review will examine the role and activation of TGases in a variety of diseases.

[Xerosis]

The clinical characteristic of xerosis is rough or coarse skin. Physiopathologically, the structure of the stratum corneum is modified and abnormalities in keratinization, proliferation, surface lipid, water metabolism and also pH and sebum exist. There are two forms of xerosis: dry skin forms and ichtyosis or ichtyosis-like forms. Xerosis has many etiologies including external aggression, senescence, drugs, infection, atopy, deficiencies, malignant diseases, endocrine affections, eating disorders and renal failure in dialyzed patients. It provokes cutaneous discomfort and unaesthetic appearance that justify appropriate treatment. Treatment is essentially local, symptomatic and must be accompanied by general measures. Many products include moisturizers and emollients (keratolytics: salicylic acid, urea and alpha-hydroxy acid).

Environmental effects on the functions of the stratum corneum

The stratum corneum (SC) is such an efficient barrier that only 2-5 g per h per cm2 of transepidermal water loss (TEWL) occurs in normal skin. The SC also plays another important role at the skin surface in keeping our skin smooth and flexible by binding water. We exposed a simulation model of in vivo SC to various, excessive physical insults in vitro, such as irradiation with 1 J per cm2 of UVB, 50 J per cm2 of UVA, or 3000 rad of X-ray, heating at 90 degrees C for 3 min, freezing at -196 degrees C for 60 s or repeated placement in an extremely dry or humid condition. None of them could cause any permanent change in the SC functions. Only the application of chemical agents such as lipid solvents or a detergent or the affliction of trauma resulted in a functional derangement of the SC. Because the viable skin tissues are more vulnerable to the effects of the environment than the SC, most of the abnormalities of the SC functions developing after environmental insults are secondarily caused by enhanced epidermal proliferation induced under the influence of underlying inflammation. These functional abnormalities were found to be demonstrable with biophysical measurements long after the disappearance of skin redness, the clinically observable sign of inflammation. The SC abnormalities in inflamed skin are also detectable as a change in the content of chemical mediators. For example, the ratio between proinflammatory IL-1 and its receptor antagonist (IL-1ra) whose production by epidermal keratinocytes is markedly enhanced by various proinflammatory stimuli, showed a deviation towards an excess of the latter in inflammatory skin. Facial skin that is always exposed to the environment is unique in that its SC shows such a deviation in the IL-1/IL-1ra ratio suggestive for the presence of mild inflammation even in normal individuals.

Identification, by homozygosity mapping, of a novel locus for autosomal recessive congenital ichthyosis on chromosome 17p, and evidence for further genetic heterogeneity

Autosomal recessive congenital ichthyosis (ARCI) comprises a group of severe disorders of keratinization, characterized by variable erythema and skin scaling. It is known for its high degree of genetic and clinical heterogeneity. Mutations in the gene for keratinocyte transglutaminase (TGM1) on chromosome 14q11 were shown in patients with ARCI, and a second locus was described, on chromosome 2q, in families from northern Africa. Three other loci for ARCI, on chromosomes 3p and 19p, were identified recently. We have embarked on a whole-genome scan for further loci for ARCI in four families from Germany, Turkey, and the United Arab Emirates. A novel ARCI locus was identified on chromosome 17p, between the markers at D17S938 and D17S1856, with a maximum LOD score of 3.38, at maximum recombination fraction 0.00, at D17S945, under heterogeneity. This locus is linked to the disease in the Turkish family and in the German family. Extensive genealogical studies revealed that the parents of the German patients with ARCI were eighth cousins. By homozygosity mapping, the localization of the gene could then be refined to the 8.4-cM interval between D17S938 and D17S1879. It could be shown, however, that ARCI in the two Arab families is linked neither to the new locus on chromosome 17p nor to one of the five loci known previously. Our findings give evidence of further genetic heterogeneity that is not linked to distinctive phenotypes.

Evidence for novel functions of the keratin tail emerging from a mutation causing ichthyosis hystrix

Unraveling the molecular basis of inherited disorders of epithelial fragility has led to understanding of the complex structure and function of keratin intermediate filaments. Keratins are organized as a central alpha-helical rod domain flanked by nonhelical, variable end domains. Pathogenic mutations in 19 different keratin genes have been identified in sequences corresponding to conserved regions at the beginning and end of the rod. These areas have been recognized as zones of overlap between aligned keratin proteins and are thought to be crucial for proper assembly of keratin intermediate filaments. Consequently, all keratin disorders of skin, hair, nail, and mucous membranes caused by mutations in rod domain sequences are characterized by perinuclear clumping of fragmented keratin intermediate filaments, thus compromising mechanical strength and cell integrity. We report here the first mutation in a keratin gene (KRT1) that affects the variable tail domain (V2) and results in a profoundly different abnormality of the cytoskeletal architecture leading to a severe form of epidermal hyperkeratosis known as ichthyosis hystrix Curth-Macklin. Structural analyses disclosed a failure in keratin intermediate filament bundling, retraction of the cytoskeleton from the nucleus, and failed translocation of loricrin to the desmosomal plaques. These data provide the first in vivo evidence for the crucial role of a keratin tail domain in supramolecular keratin intermediate filament organization and barrier formation.

Efficacy of urea therapy in children with ichthyosis. A multicenter randomized, placebo-controlled, double-blind, semilateral study

BACKGROUND

Ichthyoses are genetic disorders of keratinization which are uncomfortable due to their conspicuous scaling, itching and cosmetic problems. Especially in childhood, ichthyoses can lead to social discrimination and psychological problems. Efficient therapies are necessary which are safe and well tolerated.

OBJECTIVE

The aim of the study was to investigate the keratolytic and moisturizing properties as well as the tolerance of a new urea lotion when applied to hyperkeratotic and ichthyotic skin in childhood.

METHODS

The study was conducted as a multicenter, randomized, placebo-controlled, double-blind, semilateral investigation. Sixty children between 1 and 16 years treated one side of the most affected extremity with Laceran 10% urea lotion for 8 weeks. On the other side the urea-free Laceran lotion base was given. On each side of the body a control area was left untreated. The investigators evaluated the global severity of ichthyotic symptoms with the help of a visual analogue scale.

RESULTS

The analysis of the global estimation of severity of ichthyosis showed improvements being stronger in the body areas treated with Laceran 10% urea lotion (from 4.8 to 2.0 points) than in the areas treated with the urea-free Laceran lotion base (from 4.8 to 2.5 points). The response rates were 65% after 4 weeks and 78% after 8 weeks for Laceran 10% urea lotion, 50% after 4 weeks and 72% after 8 weeks for the urea-free Laceran lotion base.

CONCLUSION

It can be ascertained that Laceran 10% urea lotion has a strong positive effect on generalized ichthyotic keratinization disorders.

Localization of the Netherton syndrome gene to chromosome 5q32, by linkage analysis and homozygosity mapping

Netherton syndrome (NS [MIM 256500]) is a rare and severe autosomal recessive disorder characterized by congenital ichthyosis, a specific hair-shaft defect (trichorrhexis invaginata), and atopic manifestations. Infants with this syndrome often fail to thrive; life-threatening complications result in high postnatal mortality. We report the assignment of the NS gene to chromosome 5q32, by linkage analysis and homozygosity mapping in 20 families affected with NS. Significant evidence for linkage (maximum multipoint LOD score 10.11) between markers D5S2017 and D5S413 was obtained, with no evidence for locus heterogeneity. Analysis of critical recombinants mapped the NS locus between markers D5S463 and D5S2013, within an <3.5-cM genetic interval. The NS locus is telomeric to the cytokine gene cluster in 5q31. The five known genes encoding casein kinase Ialpha, the alpha subunit of retinal rod cGMP phosphodiesterase, the regulator of mitotic-spindle assembly, adrenergic receptor beta2, and the diastrophic dysplasia sulfate-transporter gene, as well as the 38 expressed-sequence tags mapped within the critical region, are not obvious candidates. Our study is the first step toward the positional cloning of the NS gene. This finding promises a better understanding of the molecular mechanisms that control epidermal differentiation and immunity.

The pathogenesis of severe congenital ichthyosis of the neonate

Severe congenital ichthyosis of the neonate include several major subtypes, i.e. harlequin ichthyosis, lamellar ichthyosis (LI), and congenital ichthyosiform erythroderma. Knowledge of the pathogenetic mechanisms is significant for the precise diagnosis, treatment, genetic counseling and prenatal diagnosis. This article reviews recent advances in studies on genetic defects and pathogenetic mechanisms of these severe congenital ichthyosis and, in addition, discuss the feasibility and methods of their prenatal diagnosis. Recently, reduced activity of the serine/threonine protein phosphatase in keratinocytes was suggested to be the cause of harlequin ichthyosis. In some families of LI, transglutaminase 1 gene mutations were identified as causative genetic defects and transglutaminase 1 is thought to be one of the candidate molecules for non-bullous congenital ichthyosiform erythroderma (NBCIE). Genotype/phenotype correlation in bullous congenital ichthyosis is now being clarified. Mutations within the rod domain, not in the beginning or the end of the rod domain, of keratin 10 were reported in annular epidermolytic ichthyosis (AEI), the distinct subtype of bullous congenital ichthyosiform erythroderma.

Association in the same patient of autosomal dominant progressive external ophthalmoplegia with multiple mtDNA deletions and X-linked ichthyosis: clinical, biochemical, histological, submicroscopic and molecular genetic study

Autosomal dominant chronic progressive external ophthalmoplegia (AdPEO) is a muscle mitochondrial disorder due to multiple large scale rearrangements of the mitochondrial DNA. This disorder is probably due to a nuclear defect which causes genetic instability or an impairment in the replication of mitochondrial DNA. X-linked ichthyosis (XLI) is a skin disorder caused by a deletion in the steroid-sulphatase gene. Here we report the clinical, biochemical, morphologic and molecular genetic findings in a patient affected by both AdPEO, inherited by the father, and steroid-sulphatase-deficiency, inherited by the mother. The association in the same patient of the two inherited diseases is merely casual and does not seem to influence the phenotypic expression of the two diseases.

Genetic skin diseases

Recent advances in molecular genetics have led to major breakthroughs in the understanding of two heterogeneous groups of inherited skin diseases, epidermolysis bullosa and the ichthyoses. Mutations in keratins K5 or K14 are found in epidermolysis bullosa simplex. The gravis (Herlitz) variety of junctional epidermolysis bullosa is characterized by defects in the anchoring filament protein kalinin. Both dominant and recessive forms of dystrophic epidermolysis bullosa appear to be due to mutations in the type VII collagen gene. Biochemical studies in patients with ichthyosis vulgaris reveal that the proteins profilaggrin and filaggrin are reduced or absent. Recessive X-linked ichthyosis is characterized by a deficiency of the enzyme steroid sulfatase. A type of lamellar ichthyosis may be explained on the basis of abnormal cornified cell envelope formation, and bullous congenital ichthyosiform erythroderma (epidermolytic hyperkeratosis) is caused by mutations in keratins K1 or K10.