CHILD syndrome caused by deficiency of 3beta-hydroxysteroid-delta8, delta7-isomerase

MSMO1 deficiency: a potentially partially treatable, ultrarare neurodevelopmental disorder with psoriasiform dermatitis, alopecia and polydactyly

MSMO1 deficiency (OMIM #616834) is an ultrarare autosomal recessive disorder of distal cholesterol metabolism with only five cases reported to date. The disorder is caused by missense variants in the MSMO1 gene encoding methylsterol monooxygenase 1, leading to the accumulation of methylsterols. Clinically, MSMO1 deficiency is characterized by growth and developmental delay, often in association with congenital cataracts, microcephaly, psoriasiform dermatitis and immune dysfunction. Treatment with oral and topical cholesterol supplements and statins was reported to improve the biochemical, immunological, and cutaneous findings, supporting a potential treatment following the precision diagnosis of MSMO1 deficiency. We describe two siblings from a consanguineous family presenting with novel clinical features of polydactyly, alopecia and spasticity. Whole-exome sequencing revealed a novel, homozygous c.548A > C, p.(Glu183Ala) variant. Based on previously published treatment algorithms, we initiated a modified dosage regime with systemic cholesterol supplementation, statins and bile acid along with topical application of a cholesterol/statin formulation. This resulted in a marked improvement of psoriasiform dermatitis and some hair growth.

Novel NSDHL gene variant for congenital hemidysplasia with ichthyosiform erythroderma and limb defects (CHILD) syndrome

We report a case of a 1-year and 2-month-old girl with clinical features consistent with congenital hemidysplasia with ichthyosis and limb defects syndrome. Sterol analysis from skin flakes revealed increased levels of a mono 4-alpha methyl sterol also seen in plasma as well as the presence of 4-alpha-carboxy-4-methyl-cholest-8(9)-en-3beta-ol and several keto-sterols, which are usually below the limit of detection. This sterol pattern is consistent with abnormal function of the 4-alpha-methylsterol-4-demethylase complex. NSDHL gene testing revealed the presence of a variant of uncertain significance, c.130G>A (p.Gly44Ser). This missense mutation currently is not included in population databases (ExAC no frequency) and has not been reported in individuals with an NSDHL-related condition. Parental studies showed that neither parent carries the NSDHL variant. On this basis, this variant has been reclassified as likely pathogenic. Symptomatic treatment with keratolytic agents, emollients and ketoconazole was initiated.

Overcoming Drug Resistance by Taking Advantage of Physical Principles: Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)

Theoretical considerations as well as comprehensive preclinical and clinical data suggest that optimizing physical parameters of intraperitoneal drug delivery might help to circumvent initial or acquired resistance of peritoneal metastasis (PM) to chemotherapy. Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) is a novel minimally invasive drug delivery system systematically addressing the current limitations of intraperitoneal chemotherapy. The rationale behind PIPAC is: (1) optimizing homogeneity of drug distribution by applying an aerosol rather than a liquid solution; (2) applying increased intraperitoneal hydrostatic pressure to counteract elevated intratumoral interstitial fluid pressure; (3) limiting blood outflow during drug application; (4) steering environmental parameters (temperature, pH, electrostatic charge etc.) in the peritoneal cavity for best tissue target effect. In addition, PIPAC allows repeated application and objective assessment of tumor response by comparing biopsies between chemotherapy cycles. Although incompletely understood, the reasons that allow PIPAC to overcome established chemoresistance are probably linked to local dose intensification. All pharmacological data published so far show a superior therapeutic ratio (tissue concentration/dose applied) of PIPAC vs. systemic administration, of PIPAC vs. intraperitoneal liquid chemotherapy, of PIPAC vs. Hyperthermic Intraperitoneal Chemotherapy (HIPEC) or PIPAC vs. laparoscopic HIPEC. In the initial introduction phase, PIPAC has been used in patients who were quite ill and had already failed multiple treatment regimes, but it may not be limited to that group of patients in the future. Rapid diffusion of PIPAC in clinical practice worldwide supports its potential to become a game changer in the treatment of chemoresistant isolated PM of various origins.

Male CDPX2 patient with EBP mosaicism and asymmetrically lateralized skin lesions with strict midline demarcation

X-linked dominant chondrodysplasia punctata (Conradi-Hunermann-Happle syndrome, CDPX2) caused by mutations in the emopamil-binding protein (EBP) gene and congenital hemidysplasia with ichthyosiform nevus and limb defects (CHILD) syndrome caused by mutation in the NAD(P)H steroid dehydrogenase-like (NSDHL) gene are rare, typically male lethal disorders. CDPX2 skin lesions are characterized by transient severe congenital ichthyosis following the lines of Blaschko, whereas in CHILD syndrome, the lesions show striking lateralization. Here, we report a male CDPX2 patient with postzygotic mosaicism of the EBP gene presenting with lateralized skin lesions with strict midline demarcation as seen in CHILD syndrome (although this diagnosis was ruled out based on analysis of NSDHL), but also partly distributed along Blaschko's lines as seen in CDPX2. The lesions resolved within a few months, but the patient had other abnormalities, including shortening of the limbs, epiphyseal stippling, and forearm asymmetry; he also had problems with respiration and feeding in the first 4 years after birth. Kyphoscoliosis with dysplastic vertebral bodies progressed rapidly and required posterior spinal fusion surgery at 6 years old. These findings provide insights into the pathophysiology of CDPX2 and the mechanism of asymmetric lesion formation during development.

A rare case of sterol-C4-methyl oxidase deficiency in a young Italian male: Biochemical and molecular characterization

Inborn defects of cholesterol biosynthesis are metabolic disorders presenting with multi-organ and tissue anomalies. An autosomal recessive defect involving the demethylating enzyme C4-methyl sterol (SC4MOL) has been reported in only 4 patients so far. In infancy, all patients were affected by microcephaly, bilateral congenital cataracts, growth delay, psoriasiform dermatitis, immune dysfunction, and intellectual disability. Herein, we describe a new case of SC4MOL deficiency in which a 19-year-old Italian male was affected by bilateral congenital cataracts, growth delay and learning disabilities, behavioral disorders and small stature, but not microcephaly. Our patient had abundant scalp dandruff, without other skin manifestations. Analysis of the blood sterol profile showed accumulation of C4-monomethyl and C4-dimethyl sterols suggesting a deficiency of the SC4MOL enzyme. Sequencing of the MSMO1 gene (also known as the "SC4MOL" gene) confirmed mutations in each allele (c.731A>G, p.Y244C, which is already known, and c.605G>A, p.G202E, which is a novel variant). His father carried c.731A>G mutation, whereas his mother carried c.605G>A. Thus, the combination of multiple skills and methodologies, in particular, blood sterol profiling and genetic analysis, led to the diagnosis of a new case of a very rare defect of cholesterol biosynthesis. Consequently, we suggest that these two analyses should be performed as soon as possible in all undiagnosed patients affected by bilateral cataracts and developmental delay.

Radiographic features of the skeleton in disorders of post-squalene cholesterol biosynthesis

Disorders of post-squalene cholesterol biosynthesis are inborn errors of metabolism characterised by multiple congenital abnormalities, including significant skeletal involvement. The most frequent and best-characterised example is the Smith-Lemli-Opitz syndrome. Nine other disorders are known, namely autosomal-recessive Antley-Bixler syndrome, Greenberg dysplasia, X-linked dominant chondrodysplasia punctata, X-linked recessive male emopamil-binding protein deficiency, CHILD syndrome, CK syndrome, sterol C4 methyloxidase-like deficiency, desmosterolosis and lathosterolosis. This study provides an overview of the radiologic features observed in these diseases. A common pattern of limb abnormalities is recognisable, including polydactyly, which is typically post-axial and rarely interdigital and can involve all four limbs, and syndactyly of the toes. Chondrodysplasia punctata is specifically associated with a subgroup of disorders of cholesterol biosynthesis (Greenberg dysplasia, CHILD syndrome, X-linked dominant chondrodysplasia punctata, male emopamil-binding protein deficiency). The possible occurrence of epiphyseal stippling in the Smith-Lemli-Opitz syndrome, initially reported, does not appear to be confirmed. Stippling is also associated with other congenital disorders such as chromosomal abnormalities, brachytelephalangic chondrodysplasia punctata (X-linked recessive chondrodysplasia punctata, disruptions of vitamin K metabolism, maternal autoimmune diseases), rhizomelic chondrodysplasia punctata (peroxisomal disorders) and lysosomal storage disorders. In the differential diagnosis of epiphyseal stippling, a moth-eaten appearance of bones, asymmetry, or presence of a common pattern of limb abnormalities indicate inborn errors of cholesterol biosynthesis. We highlight the specific differentiating radiologic features of disorders of post-squalene cholesterol biosynthesis.

The role of abnormalities in the distal pathway of cholesterol synthesis in the Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects (CHILD) syndrome

CHILD syndrome (Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects) is a rare X-linked dominant ichthyotic disorder. CHILD syndrome results from loss of function mutations in the NSDHL gene, which leads to inhibition of cholesterol synthesis and accumulation of toxic metabolic intermediates in affected tissues. The CHILD syndrome skin is characterized by plaques topped by waxy scales and a variety of developmental defects in extracutaneous tissues, particularly limb hypoplasia or aplasia. Strikingly, these alterations are commonly segregated to either the right or left side of the body midline with little to no manifestations on the ipsilateral side. By understanding the underlying disease mechanism of CHILD syndrome, a pathogenesis-based therapy has been developed that successfully reverses the CHILD syndrome skin phenotype and has potential applications to the treatment of other ichthyoses. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

Pathogenesis-based therapies in ichthyoses

During the past 20 years, tremendous progress has been made in our understanding of the molecular basis of many genetic skin conditions. The translation of these laboratory findings into effective therapies for affected individuals has been slow, however, in large part due to the risk of carcinogenesis from random viral genomic integration and the lack of efficacy of topically applied genetic material and most proteins. As intervention at the gene level still appears remote for most genetic disorders, increased knowledge about the cellular and biochemical pathogenesis of disease allows specific targeting of pathways with existing and/or novel drugs and molecules. In contrast to the requirement for personalization of most gene-based approaches, pathogenesis-based therapy is pathway specific, and in theory, it should have broader applicability. In this chapter, we provide an overview of the pathoetiology of the various types of ichthyoses and demonstrate how a pathogenesis-based approach can potentially lead to innovative treatments for these conditions. Notably, this strategy has been successfully validated for the treatment of the rare X-linked dominant condition, CHILD syndrome, in which topical applications of cholesterol and lovastatin together to affected skin resulted in marked improvement of the skin phenotype.

Disorders of sterol synthesis: beyond Smith-Lemli-Opitz syndrome

Since the discovery in 1993 that Smith-Lemli-Opitz syndrome (SLOS) is a disorder of cholesterol biosynthesis, human disorders associated with additional enzymes involved in the conversion of lanosterol to cholesterol have been identified. This review will focus primarily on the clinical aspects of these disorders, highlighting newly described syndromes, such as SC4MOL deficiency and CK syndrome. We will also provide clinical descriptions of additional cases for extremely rare disorders, such as desmosterolosis. We will compare and contrast the findings with those found in SLOS and briefly discuss possible mechanisms of disease pathogenesis.

Abnormal barrier function in the pathogenesis of ichthyosis: therapeutic implications for lipid metabolic disorders

Ichthyoses, including inherited disorders of lipid metabolism, display a permeability barrier abnormality in which the severity of the clinical phenotype parallels the prominence of the barrier defect. The pathogenesis of the cutaneous phenotype represents the consequences of the mutation for epidermal function, coupled with a "best attempt" by affected epidermis to generate a competent barrier in a terrestrial environment. A compromised barrier in normal epidermis triggers a vigorous set of metabolic responses that rapidly normalizes function, but ichthyotic epidermis, which is inherently compromised, only partially succeeds in this effort. Unraveling mechanisms that account for barrier dysfunction in the ichthyoses has identified multiple, subcellular, and biochemical processes that contribute to the clinical phenotype. Current treatment of the ichthyoses remains largely symptomatic: directed toward reducing scale or corrective gene therapy. Reducing scale is often minimally effective. Gene therapy is impeded by multiple pitfalls, including difficulties in transcutaneous drug delivery, high costs, and discomfort of injections. We have begun to use information about disease pathogenesis to identify novel, pathogenesis-based therapeutic strategies for the ichthyoses. The clinical phenotype often reflects not only a deficiency of pathway end product due to reduced-function mutations in key synthetic enzymes but often also accumulation of proximal, potentially toxic metabolites. As a result, depending upon the identified pathomechanism(s) for each disorder, the accompanying ichthyosis can be treated by topical provision of pathway product (eg, cholesterol), with or without a proximal enzyme inhibitor (eg, simvastatin), to block metabolite production. Among the disorders of distal cholesterol metabolism, the cutaneous phenotype in Congenital Hemidysplasia with Ichthyosiform Erythroderma and Limb Defects (CHILD syndrome) and X-linked ichthyosis reflect metabolite accumulation and deficiency of pathway product (ie, cholesterol). We validated this therapeutic approach in two CHILD syndrome patients who failed to improve with topical cholesterol alone, but cleared with dual treatment with cholesterol plus lovastatin. In theory, the ichthyoses in other inherited lipid metabolic disorders could be treated analogously. This pathogenesis (pathway)-driven approach possesses several inherent advantages: (1) it is mechanism-specific for each disorder; (2) it is inherently safe, because natural lipids and/or approved drugs often are utilized; and (3) it should be inexpensive, and therefore it could be used widely in the developing world.

Pathogenesis-based therapy reverses cutaneous abnormalities in an inherited disorder of distal cholesterol metabolism

Identification of the underlying genetic, cellular, and biochemical basis of lipid metabolic disorders provides an opportunity to deploy corrective, mechanism-targeted, topical therapy. We assessed this therapeutic approach in two patients with Congenital Hemidysplasia with Ichthyosiform Erythroderma and Limb Defects (CHILD) syndrome, an X-linked dominant disorder of distal cholesterol metabolism. Based upon the putative pathogenic role of both pathway-product deficiency of cholesterol and accumulation of toxic metabolic intermediates, we assessed the efficacy of combined therapy with lovastatin and cholesterol. We also evaluated the basis for the poorly understood, unique lateralization of the cutaneous and bone malformations of CHILD syndrome by analyzing gene activation in abnormal and unaffected skin. Ultrastructural analysis of affected skin showed evidence of both cholesterol depletion and toxic metabolic accumulation. Topical treatment with lovastatin/cholesterol (but not cholesterol alone) virtually cleared skin lesions by 3 months, accompanied by histologic and ultrastructural normalization of epidermal structure and lipid secretion. The unusual lateralization of abnormalities in CHILD syndrome reflects selective clearance of keratinocytes and fibroblasts that express the mutant allele from the unaffected side. These findings validate pathogenesis-based therapy that provides the deficient end-product and prevents accumulation of toxic metabolites, an approach of potential utility for other syndromic lipid metabolic disorders.

Pathogenesis of the cutaneous phenotype in inherited disorders of cholesterol metabolism: Therapeutic implications for topical treatment of these disorders

Molecular geneticists tend to conceptualize disease pathogenesis from the mutated gene outward, an approach that does not take into account the impact of barrier requirements in determining disease phenotype. An ‘outside-to-inside’ perspective has provided quite different explanations for the ichthyoses, including several of the disorders of distal cholesterol metabolism. Elucidation of responsible pathogenic mechanisms also is pointing to appropriate, pathogenesis (pathway)-based therapeutic strategies. In the case of the lipid metabolic disorders, it takes full advantage of new molecular, genetic and cellular pathogenesis information to correct or bypass the metabolic abnormality. This approach fully exploits the unique accessibility of the skin to a topical approach. Moreover, since it will utilize topical lipids and lipid-soluble, and often generic, lipid-soluble drugs, these treatments should be readily transported across the stratum corneum. If successful, this approach could initiate an entirely new departure for the therapy of the ichthyoses. Finally, because these agents are relatively safe and inexpensive, this form of treatment has the potential to be widely-deployed, even in the developing world.

Malformation syndromes caused by disorders of cholesterol synthesis

Cholesterol homeostasis is critical for normal growth and development. In addition to being a major membrane lipid, cholesterol has multiple biological functions. These roles include being a precursor molecule for the synthesis of steroid hormones, neuroactive steroids, oxysterols, and bile acids. Cholesterol is also essential for the proper maturation and signaling of hedgehog proteins, and thus cholesterol is critical for embryonic development. After birth, most tissues can obtain cholesterol from either endogenous synthesis or exogenous dietary sources, but prior to birth, the human fetal tissues are dependent on endogenous synthesis. Due to the blood-brain barrier, brain tissue cannot utilize dietary or peripherally produced cholesterol. Generally, inborn errors of cholesterol synthesis lead to both a deficiency of cholesterol and increased levels of potentially bioactive or toxic precursor sterols. Over the past couple of decades, a number of human malformation syndromes have been shown to be due to inborn errors of cholesterol synthesis. Herein, we will review clinical and basic science aspects of Smith-Lemli-Opitz syndrome, desmosterolosis, lathosterolosis, HEM dysplasia, X-linked dominant chondrodysplasia punctata, Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects Syndrome, sterol-C-4 methyloxidase-like deficiency, and Antley-Bixler syndrome.

The group of epidermal nevus syndromes Part I. Well defined phenotypes

The epidermal nevus syndromes represent a group of distinct disorders that can be distinguished by the type of associated epidermal nevus and by the criterion of presence or absence of heritability. Well defined syndromes characterized by organoid epidermal nevi include Schimmelpenning syndrome, phacomatosis pigmentokeratotica, nevus comedonicus syndrome, angora hair nevus syndrome, and Becker nevus syndrome. The molecular basis of these disorders has so far not been identified. By contrast, the group of syndromes characterized by keratinocytic nevi comprises three phenotypes with a known molecular etiology in the form of CHILD (congenital hemidysplasia with ichthyosiform nevus and limb defects) syndrome, type 2 segmental Cowden disease, and fibroblast growth factor receptor 3 epidermal nevus syndrome (García-Hafner-Happle syndrome), whereas Proteus syndrome is still of unknown origin. From this overview, it is clear that a specific type of these disorders cannot be classified by the name "epidermal nevus syndrome" nor by the terms "organoid nevus syndrome" or "keratinocytic nevus syndrome."

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to distinguish nine different epidermal nevus syndromes by their characteristic features, understand the practical significance of avoiding terms like "epidermal nevus syndrome" or "keratinocytic nevus syndrome" to define any specific entity within this group of disorders, and differentiate between nonhereditary traits and those bearing a genetic risk because of either Mendelian or non-Mendelian inheritance.

Developmental expression pattern of the cholesterogenic enzyme NSDHL and negative selection of NSDHL-deficient cells in the heterozygous Bpa(1H)/+ mouse

NSDHL (NAD(P)H sterol dehydrogenase-like), is a 3beta-hydroxysterol dehydrogenase thought to function in the demethylation of sterol precursors in one of the later steps of cholesterol biosynthesis. Mutations in the X-linked NSDHL gene cause CHILD syndrome in humans, and the male-lethal bare patches (Bpa) phenotype in mice. The relative level of NSDHL expression among different mouse tissues at several stages of embryogenesis and postnatal development was analyzed by immunohistochemistry. In wild type (WT) embryos, the highest levels of expression were seen in the liver, dorsal root ganglia, central nervous system, retina, adrenal gland and testis. Heterozygous Bpa(1H) females are mosaic for NSDHL expression due to normal random X-inactivation. NSDHL-deficient cells were detected in the developing cerebral cortex and retina of Bpa(1H) female embryos. In postnatal WT and Bpa(1H) animals, we compared the expression pattern of NSDHL in skin, an affected tissue; liver, a main site of cholesterol synthesis; and brain, a tissue dependent on endogenous synthesis of cholesterol due to lack of transport across the blood-brain barrier. Clonal populations of mutant cells were visible in the brain, skin and liver of Bpa(1H) pups. In the liver, the proportion of NSDHL negative cells dropped from approximately 50% at postnatal day 6 to approximately 20% at one year of age. In the brain, which showed the highest expression in cerebral cortical and hippocampal neurons, the proportion of NSDHL negative cells also dropped dramatically over the first year of life. Our results suggest that while NSDHL-deficient cells in the mosaic Bpa(1H) female are able to survive and differentiate during embryonic development, they are subject to negative selection over the life of the animal.

Chondrodysplasia punctata: a clinical diagnostic and radiological review

Chondrodysplasia punctata (CDP) is associated with a number of disorders, including inborn errors of metabolism, involving peroxisomal and cholesterol pathways, embryopathy and chromosomal abnormalities. Several classification systems of the different types of CDP have been suggested earlier. More recently, the biochemical and molecular basis of a number of CDP syndromes has recently been elucidated and a new aetiological classification has emerged. Here we provide an updated version with an overview of the different types of CDP, a discussion of the aetiology and a description of the clinical and radiographic findings. An investigative guideline to help determine the exact diagnosis in new cases is also presented.

Identification of essential amino acid residues in a sterol 8,7-isomerase from Zea mays reveals functional homology and diversity with the isomerases of animal and fungal origin

A putative 8,7SI (sterol 8,7-isomerase) from Zea mays, termed Zm8,7SI, has been isolated from an EST (expressed sequence tag) library and subcloned into the yeast erg2 mutant lacking 8,7SI activity. Zm8,7SI restored endogenous ergosterol synthesis. An in vitro enzymatic assay in the corresponding yeast microsomal extract indicated that the preferred Delta(8)-sterol substrate possesses a single C4alpha methyl group, in contrast with 8,7SIs from animals and fungi, thus reflecting the diversity in the structure of their active site in relation to the distinct sterol biosynthetic pathways. In accordance with the proposed catalytic mechanism, a series of lipophilic ammonium-ion-containing derivatives possessing a variety of structures and biological properties, potently inhibited the Zm8,7SI in vitro. To evaluate the importance of a series of conserved acidic and tryptophan residues which could be involved in the Zm8,7SI catalytic mechanism, 20 mutants of Zm8,7SI were constructed as well as a number of corresponding mutants of the Saccharomyces cerevisiae 8,7SI. The mutated isomerases were assayed in vivo by sterol analysis and quantification of Delta(5,7)-sterols and directly in vitro by examination of the activities of the recombinant Zm8,7SI mutants. These studies have identified His(74), Glu(78), Asp(107), Glu(121), Trp(66) and Trp(193) that are required for Zm8,7SI activity and show that binding of the enzyme-substrate complex is impaired in the mutant T124I. They underline the functional homology between the plant and animal 8,7SIs on one hand, in contrast with the yeast 8,7SI on the other hand, in accordance with their molecular diversity and distinct mechanisms.

Pathogenesis of permeability barrier abnormalities in the ichthyoses: inherited disorders of lipid metabolism

Many of the ichthyoses are associated with inherited disorders of lipid metabolism. These disorders have provided unique models to dissect physiologic processes in normal epidermis and the pathophysiology of more common scaling conditions. In most of these disorders, a permeability barrier abnormality "drives" pathophysiology through stimulation of epidermal hyperplasia. Among primary abnormalities of nonpolar lipid metabolism, triglyceride accumulation in neutral lipid storage disease as a result of a lipase mutation provokes a barrier abnormality via lamellar/nonlamellar phase separation within the extracellular matrix of the stratum corneum (SC). Similar mechanisms account for the barrier abnormalities (and subsequent ichthyosis) in inherited disorders of polar lipid metabolism. For example, in recessive X-linked ichthyosis (RXLI), cholesterol sulfate (CSO(4)) accumulation also produces a permeability barrier defect through lamellar/nonlamellar phase separation. However, in RXLI, the desquamation abnormality is in part attributable to the plurifunctional roles of CSO(4) as a regulator of both epidermal differentiation and corneodesmosome degradation. Phase separation also occurs in type II Gaucher disease (GD; from accumulation of glucosylceramides as a result of to beta-glucocerebrosidase deficiency). Finally, failure to assemble both lipids and desquamatory enzymes into nascent epidermal lamellar bodies (LBs) accounts for both the permeability barrier and desquamation abnormalities in Harlequin ichthyosis (HI). The barrier abnormality provokes the clinical phenotype in these disorders not only by stimulating epidermal proliferation, but also by inducing inflammation.

A Botrytis cinerea emopamil binding domain protein, required for full virulence, belongs to a eukaryotic superfamily which has expanded in euascomycetes

A previous transcriptomic analysis of 3,032 fungal genes identified the Botrytis cinerea PIE3 (BcPIE3) gene to be up-regulated early in planta (A. Gioti, A. Simon, P. Le Pêcheur, C. Giraud, J. M. Pradier, M. Viaud, and C. Levis, J. Mol. Biol. 358:372-386, 2006). In the present study, BcPIE3 was disrupted in order to determine its implication in pathogenicity. BcPIE3 was shown to be a virulence factor, since the DeltaBcPIE3 mutant was blocked during the colonization of tomato and bean leaves, giving lesions reduced in size by at least 74%. Within the emopamil binding domain (EBD), BcPIE3 shows significant structural similarities to mammalian emopamil binding proteins (EBPs). Mammalian EBPs function as sterol isomerases, but an analysis of the sterol content and the results of growth inhibition experiments with the DeltaBcPIE3 strain indicated that BcPIE3 is dispensable for ergosterol biosynthesis. The systematic identification of EBD-containing proteins included in public databases showed that these proteins constitute a protein superfamily present only in eukaryotes. Phylogenetic analysis showed that the ancestral EBD-encoding gene was duplicated in the common ancestor of animals and fungi after the split from plants. Finally, we present evidence that the EBP phylogenetic clade of this superfamily has further expanded exclusively in euascomycetes, especially in B. cinerea, which contains three copies of the EBP gene.

Reduced penetrance in a family with X-linked dominant chondrodysplasia punctata

X-linked dominant chondrodysplasia punctata (Conradi-Hünermann disease, CDPX2) is characterised by short stature, stippled epiphyses, cataracts, ichthyosiform erythroderma and patchy alopecia of the scalp. The disorder is caused by mutations within the emopamil binding protein (EBP) gene encoding a 3beta-hydroxysteroid-Delta(8),Delta(7)-isomerase. The intrafamilial variation of disease severity is a known feature of CDPX2 probably caused by skewed X-inactivation. We report on a female fetus with typical symptoms of CDPX2 such as short limbs, postaxial polydactyly, ichthyotic skin lesions and punctate calcifications. Molecular genetic analysis of the EBP gene revealed a nonsense mutation (c.328C>T, p.R110X), which was previously detected in one CDPX2 patient and in a second female patient, who was only affected on one body side and erroneously diagnosed as CHILD syndrome. Surprisingly, the mother of our fetus carries the same mutation without having any signs of CDPX2. X-inactivation studies did not reveal any evidence of skewing neither in the mother nor in the fetus.

Recent insights into the Smith-Lemli-Opitz syndrome

Recent insights into the Smith-Lemli-Opitz syndrome. The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple congenital anomaly/mental retardation disorder caused by an inborn error of post-squalene cholesterol biosynthesis. Deficient cholesterol synthesis in SLOS is caused by inherited mutations of 3beta-hydroxysterol-Delta7 reductase gene (DHCR7). DHCR7 deficiency impairs both cholesterol and desmosterol production, resulting in elevated 7DHC/8DHC levels, typically decreased cholesterol levels and, importantly, developmental dysmorphology. The discovery of SLOS has led to new questions regarding the role of the cholesterol biosynthesis pathway in human development. To date, a total of 121 different mutations have been identified in over 250 patients with SLOS who represent a continuum of clinical severity. Two genetic mouse models have been generated which recapitulate some of the developmental abnormalities of SLOS and have been useful in elucidating the pathogenesis. This mini review summarizes the recent insights into SLOS genetics, pathophysiology and potential therapeutic approaches for the treatment of SLOS.

The expression of the 27-kd heat shock protein in keratinization disorders: an immunohistological study

In human skin, the 27-kd heat shock protein (hsp27), a member of the small hsp family, is expressed mainly in the upper epidermal layers. Hsp27 functions as a molecular chaperone and is involved in the regulation of cell growth and differentiation. According to experimental evidence, epidermal hsp27, through its chaperone function, might play a role in the assembly of keratin filaments and the cornified cell envelope. This study was conducted to assess the expression pattern of hsp27 in a panel of different ichthyoses. Twelve hereditary and acquired skin diseases associated with an ichthyotic phenotype and 2 corresponding mouse models were investigated by immunohistochemistry on formalin-fixed paraffin-embedded tissue, using a monoclonal antibody specific for hsp27. In ichthyosis vulgaris, lamellar ichthyosis, Sjögren-Larsson syndrome, Netherton syndrome, and acquired ichthyosiform skin condition, the pattern of hsp27 expression resembles healthy human skin. Hsp27 expression was reduced in bullous ichthyosiform erythroderma and annular epidermolytic ichthyosis, and absent in X-linked recessive ichthyosis (1/3 patients) and congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome (1/1). In X-linked dominant chondrodysplasia, 3 small samples are completely negative and 2 larger samples show a pattern resembling random X inactivation. In the mouse models, tattered and bare patches, representing the murine analogues to X-linked dominant chondrodysplasia and congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome, expression of hsp25 (the murine homologue of hsp27) also showed lyonization, demonstrating a clear-cut link between hsp27 expression and underlying molecular pathology. Our results show that loss of hsp27 is a rare event in human epidermis that is associated with specific genetic defects. Among the cases described here, these defects are either in suprabasal keratins or in enzymes involved in cholesterol biosynthesis. The expression and chaperone function of hsp27 might be modified by low/absent epidermal cholesterol and aberrant substrates (ie, keratins) resulting in protein misfolding, dyskeratosis, and thus contribute to the ichthyotic phenotype.

The cornified envelope: a model of cell death in the skin

The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.

3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome

In the final step of cholesterol synthesis, 7-dehydrocholesterol reductase (DHCR7) reduces the double bond at C7-8 of 7-dehydrocholesterol to yield cholesterol. Mutations of DHCR7 cause Smith-Lemli-Opitz syndrome (SLOS). Over 100 different mutations of DHCR7 have been identified in SLOS patients. SLOS is a classical multiple malformation, mental retardation syndrome, and was the first human malformation syndrome shown to result from an inborn error of cholesterol synthesis. This paper reviews the biochemical, molecular, and mutational aspects of DHCR7.

Sterol profiling of amniotic fluid: a routine method for the detection of distal cholesterol synthesis deficit

OBJECTIVES

Smith Lemli Opitz syndrome (SLOS) caused by a deficit of 3beta-hydroxysterol-Delta7 reductase was the first sterol deficit described with multiple malformations. The lack of specificity of many morphological abnormalities detected by ultrasound and their frequency have justified routine screening of amniotic fluid (AF) for sterols by GC-MS. The examination contributes to an improved knowledge of the sterol status in the fluid.

METHODS

A series of sterol profiles is collated here. Accumulation of 7- and 8-dehydrocholesterol are diagnostic for SLOS. However, a number of other sterols have also been detected by GC-MS in control AF and their presence may be confusing.

RESULTS AND CONCLUSIONS

In addition to cholesterol, the level of which varies as function of the gestational age, lathosterol is present together with trace amounts of 7- and 8-dehydrocholesterol and other precursors such as desmosterol, lanosterol, and dimethylsterol. Phytosterols are also present in 70% of AF samples that have been tested. Besides SLOS, GC-MS examination of amniotic fluid can detect various sterol deficits associated with malformations (lathosterolosis, desmosterolosis, X-linked chondrodysplasia, and particular Antley-Bixler syndrome). Practical conclusions support GC-MS as a routine method to investigate skeletal and central nervous system malformations.

Epidermal desquamation

Epidermal desquamation, a continuous but insensible bodily activity, is largely ignored unless the rate or amount of scale production becomes abnormal. It is the last topic to be considered in any serious discussion of epidermal growth and differentiation, but is becoming an increasingly fertile ground for investigation. This review summarizes: (a) methods for measuring desquamation; (b) variables that affect normal desquamation; (c) mechanisms of desquamation; (d) the role of desquamation in nutritional homeostasis; and (e) the role of desquamation as a first line of defense. Consideration is given to whether desquamation might be harnessed to eliminate or remediate toxins that have accumulated in the body.

Severe hemihypotrophy in a female infant with mosaic Turner syndrome: a variant of Russell-Silver syndrome?

Russell-Silver syndrome is a genetically heterogeneous condition. For most affected individuals, it represents a phenotype rather than a specific disorder. Although chromosomal anomalies, imprinting disorder, maternal uniparental disomy 7 as well as familial autosomal dominant and X-linked forms have been reported, the diagnosis remains determined on clinical grounds. Russell-Silver syndrome is characterized by asymmetric intrauterine growth retardation, postnatal failure to thrive, distinct facial features, limb asymmetry, excessive sweating and minor skin lesions. We report here a female infant who had a karyotype of 45,X on prenatal amniocytes. After delivery she was noted to have features not explainable on the basis of Turner syndrome. Her phenotype actually was quite consistent with Russell-Silver syndrome. She had a triangular face with prominent forehead, large eyes, a thin nose, malar hypoplasia, thin upper lip with down-turned corner of the mouth and a pointed chin. Marked body asymmetry was evident at birth, with the left side significantly smaller than the right side. She has a diphalangeal left fifth finger. Skin fibroblast culture and analysis showed a karyotype of 45,X on the right side and 45,X/46,XX on the left side. The case is another illustration of the genetic heterogeneity of Russell-Silver phenotype.

Late gestational lung hypoplasia in a mouse model of the Smith-Lemli-Opitz syndrome

Background

Normal post-squalene cholesterol biosynthesis is important for mammalian embryonic development. Neonatal mice lacking functional dehydrocholesterol Δ7-reductase (Dhcr7), a model for the human disease of Smith-Lemli-Opitz syndrome, die within 24 hours of birth. Although they have a number of biochemical and structural abnormalities, one cause of death is from apparent respiratory failure due to developmental pulmonary abnormalities.

Results

In this study, we characterized further the role of cholesterol deficiency in lung development of these mice. Significant growth retardation, beginning at E14.5~E16.5, was observed in Dhcr7^-/- embryos. Normal lobation but smaller lungs with a significant decrease in lung-to-body weight ratio was noted in Dhcr7^-/- embryos, compared to controls. Lung branching morphogenesis was comparable between Dhcr7^-/- and controls at early stages, but delayed saccular development was visible in all Dhcr7^-/- embryos from E17.5 onwards. Impaired pre-alveolar development of varying severity, inhibited cell proliferation, delayed differentiation of type I alveolar epithelial cells (AECs) and delayed vascular development were all evident in knockout lungs. Differentiation of type II AECs was apparently normal as judged by surfactant protein (SP) mRNAs and SP-C immunostaining. A significant amount of cholesterol was detectable in knockout lungs, implicating some maternal transfer of cholesterol. No significant differences of the spatial-temporal localization of sonic hedgehog (Shh) or its downstream targets by immunohistochemistry were detected between knockout and wild-type lungs and Shh autoprocessing occurred normally in tissues from Dhcr7^-/- embryos.

Conclusion

Our data indicated that cholesterol deficiency caused by Dhcr7 null was associated with a distinct lung saccular hypoplasia, characterized by failure to terminally differentiate alveolar sacs, a delayed differentiation of type I AECs and an immature vascular network at late gestational stages. The molecular mechanism of impaired lung development associated with sterol deficiency by Dhcr7 loss is still unknown, but these results do not support the involvement of dysregulated Shh-Patched-Gli pathway in causing this defect.

Ichthyosis and Keratotic Follicular Plugs Containing Dystrophic Calcification in Newborns

Prior to the recent characterization of the enzymatic defect and identification of the involved gene, the histopathology of X-linked dominant chondrodysplasia punctata (Conradi-Hünermann-Happle syndrome or CDPX2) has been described under various names including calcinosis universalis, chondrodystrophia calcificans congenita, Conradi disease, and Conradi-Hünermann syndrome. We present two newborns with characteristic ichthyosiform erythroderma noted at birth. Radiographs demonstrated chondrodysplasia punctata in one patient. Although the x-ray performed at birth was negative in the other patient, sterol analyses of the keratotic scales were diagnostic for CDPX2. Skin biopsies from both patients showed thick laminated orthokeratosis and prominent keratotic follicular plugs containing dystrophic calcification. We also retrospectively examined 20 cases of various types of ichthyosis seen over a 23-year period at our institution. Intracorneal calcium deposition was not seen in any of these cases. As demonstrated by our cases and review of the literature, dystrophic calcification in the keratotic plug is a distinctive histopathologic feature of Conradi-Hünermann-Happle syndrome in newborns and is not seen in other known forms of ichthyoses.

Human malformation syndromes due to inborn errors of cholesterol synthesis

PURPOSE OF REVIEW

This review covers a group of human malformation syndromes, which are caused by inborn errors of cholesterol synthesis. The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple malformation, and mental retardation syndrome that is the prototypical example of this group of disorders. In the 10 years since the biochemical cause of SLOS was identified, other malformation syndromes have been shown to result from defects in this pathway. These include desmosterolosis, lathosterolosis, X-linked dominant chondrodysplasia punctata type 2 (CDPX2), congenital hemidysplasia with ichthyosiform erythroderma and limb defects (CHILD syndrome), hydrops-ectopic calcification-moth-eaten skeletal dysplasia (HEM dysplasia), and some cases of Antley-Bixler syndrome. These disorders represent the first true merging of dysmorphology with biochemical genetics.

RECENT FINDINGS

Recent studies report the identification of human lathosterolosis patients, indicate that SLOS is a relatively common genetic disorder that may be a major unrecognized cause of fetal loss, suggest that correction of the biochemical defect can improve central nervous system function, and show that perturbed sonic hedgehog signaling due to decreased sterol levels likely underlies some of the malformations in SLOS and lathosterolosis.

SUMMARY

Recognition of the biochemical defect in these syndromes has given insight into the role that cholesterol plays during normal development, into understanding the pathophysiological processes that underlie the clinical problems found in these disorders, and into developing therapeutic interventions.

Left-sided CHILD syndrome caused by a nonsense mutation in the NSDHL gene

Congenital hemidysplasia with ichthyosiform nevus and limb defects (CHILD) syndrome is a rare X-linked dominant malformation syndrome characterized by unilaterally distributed ichthyosiform nevi, often sharply delimited at the midline, and ipsilateral limb defects. At least two-thirds of cases demonstrate involvement of the right side. Mutations in an essential enzyme of cholesterol biosynthesis, NAD(P)H steroid dehydrogenase-like [NSDHL], have been reported in five unrelated patients with right-sided CHILD syndrome and in a sixth patient with bilaterally, symmetric nevi and mild skeletal anomalies, but not with CHILD syndrome as originally defined. Although all of the molecularly diagnosed cases with the CHILD phenotype to date have had right-sided disease, we report here a novel nonsense mutation (E151X) of NSDHL in an infant with left-sided CHILD syndrome. This result demonstrates that both right- and left-sided CHILD syndrome can be caused by mutations in the same gene.

Identification of two novel mutations in the murine Nsdhl sterol dehydrogenase gene and development of a functional complementation assay in yeast

Nsdhl is a 3beta-hydroxysterol dehydrogenase that is involved in the removal of C-4 methyl groups in the cholesterol biosynthetic pathway. Mutations in this gene are associated with the X-linked male lethal mouse mutations bare patches (Bpa) and striated (Str) and human CHILD syndrome. We have now detected the missense mutations V53D and A94T in conserved amino acids in two additional Bpa alleles. The latter alters the same amino acid as a missense mutation found in two unrelated CHILD patients, strongly suggesting that differences in the phenotype between Bpa mice and females with CHILD syndrome are unlikely to be explained by different types or sites of mutations. We have also demonstrated that the mouse NSDHL protein can rescue the lethality of erg26 deficient cells of Saccharomyces cerevisiae that lack the yeast ortholog, substantiating the role of NSDHL as a C-3 sterol dehydrogenase. Using this in vivo assay, we have demonstrated that two Str alleles function as hypomorphs, while three Bpa and one Str allele provide no complementation or rescue.

MCA/MR syndrome with hypocholesterolemia related to familial dominant hypobetalipoproteinemia

Recent reports have emphasized the role of cholesterol in vertebrate embryonic development. The RSH or so-called Smith-Lemli-Opitz syndrome (SLOS) was the first multiple congenital anomalies/mental retardation syndrome related to a cholesterol synthesis disturbance. Familial hypobetalipoproteinemia is a well-known dominantly inherited entity in which affected individuals usually are free of symptoms. We report on the unusual association of a malformation syndrome with mental retardation resembling SLOS and profound hypocholesterolemia related to familial hypobetalipoproteinemia. We discuss the possible causal relationship between the two conditions and the current understanding of the role of cholesterol in normal embryogenesis.

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

Fetus with an unusual form of nonrhizomelic chondrodysplasia punctata: case report and review

Chondrodysplasia punctata (CDP) is a heterogeneous condition mainly characterized by premature and ectopic calcification of cartilage. Many genetic and nongenetic causes have been described leading to a preliminar etiological classification into defects of peroxisomal metabolism, defects in cholesterol metabolism, and vitamin K (vit K) metabolism. However, numerous cases of CDP still remain unclassified. The difficulties in reaching a causal diagnosis are illustrated here by a 23-week-old fetus with nonrhizomelic CDP characterized by extensive cartilage stippling, brachyphalangy, and nasal hypoplasia.

Biochemical abnormality associated with Smith-Lemli-Opitz syndrome in an infant with features of Rutledge multiple congenital anomaly syndrome confirms that the latter is a variant of the former

We describe a female infant with morphologic features of Rutledge multiple-congenital-anomaly syndrome (RMCAS) and biochemical features of Smith-Lemli-Opitz syndrome (SLOS). She had microcephaly with hypoplastic cerebral frontal lobes and cerebellum, agenesis of the splenium of corpus callosum, abnormal facies including hypertelorism with bilateral inner epicanthal folds, a broad nasal bridge with slightly anteverted nares and patent choanae, low set ears and complex conchal formation, high-arched palate and thick maxillary alveolar ridges, and micrognathia. Her chest was broad, genitalia were ambiguous, and uterus was bicornuate. Skeletal abnormalities included a hypoplastic appendicular skeleton, post-axial hexadactyly of the right hand and the left foot, syndactyly of bilateral 2nd-3rd toes and left 5th-6th toes, right talipes varus and left talipes valgus, and fused L5-S1 vertebrae. Congenital heart disease consisted of hypoplastic left heart, coronary sinus agenesis, ostium secundum and ostium primum defects, and a thickened septum primum. The lungs were hypolobated and the kidneys manifested oligopapillary hypoplasia. Total colonic Hirschsprung disease was noted microscopically. Analysis of liver tissue taken at postmortem examination revealed the ratio of 7-dehydrocholesterol and cholesterol to be 143 (expected, 0.28 +/- 0.28). Although initially described as a distinct syndrome, RMCAS was merged with the severe form of SLOS, because of significantly overlapping features [Online Mendelian Inheritance in Man (OMIM) #268670]. The biochemical data showing an excess of 7-dehydrocholesterol and low cholesterol in the liver tissue of our case supports this viewpoint.

International nosology and classification of constitutional disorders of bone (2001)

The last International Classification of Constitutional Disorders of Bone was published in 1998. Since then rapid advances have been made in identifying the molecular changes responsible for defined conditions and new disorders are constantly being delineated. For these reasons a further update on the classification is appropriate. It has been expended to not only the osteochondrodysplasias (33 groups) but also genetically determined dysostoses (3 groups).

Abnormal sterol metabolism in a patient with Antley-Bixler syndrome and ambiguous genitalia

Antley-Bixler syndrome (ABS) is a rare multiple anomaly syndrome comprising radiohumeral synostosis, bowed femora, fractures of the long bones, premature fusion of the calvarial sutures, severe midface hypoplasia, proptosis, choanal atresia, and, in some, ambiguous genitalia. Of fewer than 40 patients described to date, most have been sporadic, although reports of parental consanguinity and affected sibs of both sexes suggests autosomal recessive inheritance in some families. Known genetic causes among sporadic cases of ABS or ABS-like syndromes are missense mutations in the IgII and IgIII regions of FGFR2, although the assignment of the diagnosis of ABS to such children has been disputed. A third cause of an ABS-like phenotype is early in utero exposure to fluconazole, an inhibitor of lanosterol 14-alpha-demethylase. The fourth proposed cause of ABS is digenic inheritance combining heterozygosity or homozygosity for steroid 21-hydroxylase deficiency with effects from a second gene at an unknown locus. Because fluconazole is a strong inhibitor of lanosterol 14-alpha-demethylase (CYP51), we evaluated sterol metabolism in lymphoblast cell lines from an ABS patient without a known FGFR2 mutation and from a patient with an FGFR2 mutation and ABS-like manifestations. When grown in the absence of cholesterol to stimulate cholesterol biosynthesis, the cells from the ABS patient with ambiguous genitalia but without an FGFR2 mutation accumulated markedly increased levels of lanosterol and dihydrolanosterol. Although the abnormal sterol profile suggested a deficiency of lanosterol 14-alpha-demethylase, mutational analysis of its gene, CYP51, disclosed no obvious pathogenic mutation in any of its 10 exons or exon-intron boundaries. Sterol metabolism in lymphoblasts from the phenotypically unaffected mother was normal. Our results suggest that ABS can occur in a patient with an intrinsic defect of cholesterol biosynthesis at the level of lanosterol 14-alpha-demethylase, although the genetic nature of the deficiency remains to be determined.

Teratogenesis of holoprosencephaly

Teratogenic causes of holoprosencephaly are critically assessed. A brief general review of holoprosencephaly is followed by four tables summarizing etiologic factors. Subjects evaluated here include: 1) maternal diabetes; 2) ethyl alcohol; 3) retinoic acid; 4) mutated genes and teratogens involving the sonic hedgehog signaling network and cholesterol biosynthesis; and 5) cholesterol trafficking, sterol adducts, target tissue response, and sterol sensing domain.

Cholesterol storage defect in RSH/Smith-Lemli-Opitz syndrome fibroblasts

The RSH/Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation/mental retardation syndrome caused by an inborn error of cholesterol synthesis. Mutations in the 3beta-hydroxysteroid Delta(7)-reductase gene result in impaired enzymatic reduction of 7-dehydrocholesterol (7-DHC) to cholesterol. Cells obtain cholesterol by either de novo synthesis or from exogenous sources by the binding and uptake of low density lipoprotein (LDL) particles. Because de novo synthesis of cholesterol is impaired in SLOS, current investigational therapy for SLOS consists of dietary cholesterol supplementation. However, the potential effects of elevated intracellular levels of 7-DHC on intracellular LDL metabolism have not been described. We now report that in addition to the primary defect in de novo cholesterol synthesis, SLOS fibroblasts have a secondary defect of LDL cholesterol metabolism. Staining of fibroblasts with filipin, a fluorescent polyene antibiotic which binds unesterified sterols, shows that SLOS fibroblasts accumulate unesterified sterols. Further studies show that this increased filipin staining was due to an abnormal accumulation of LDL derived cholesterol rather than due to storage of endogenously synthesized 7-dehydrocholesterol (7-DHC). We have also found that SLOS fibroblasts failed to degrade LDL at a normal rate, and examination of SLOS fibroblasts by electron microscopy demonstrated the formation of lysosomal inclusions similar to that seen in Niemann-Pick type C (NPC) cells. We propose that 7-DHC may directly or indirectly inhibit the function of the NPC protein through its sterol-sensing domain (SSD), and that 7-DHC may perturb the function of other SSD containing proteins in SLOS.

A novel missense mutation of NSDHL in an unusual case of CHILD syndrome showing bilateral, almost symmetric involvement

The CHILD syndrome (MIM 308050), an acronym for congenital hemidysplasia with ichthyosiform nevus and limb defects, is an X-linked dominant trait with lethality for male embryos. Recently, we elucidated the underlying gene defect by demonstrating point mutations in NSDHL (NAD[P]H steroid dehydrogenase-like protein) at Xq28 in 6 patients with classic CHILD syndrome. The most striking clinical feature is an inflammatory nevus that usually shows a unique lateralization with strict midline demarcation. Ipsilateral defects involve all skeletal structures and internal organs such as the brain, the lung, the heart, or the kidney. As an exception to this rule, in some cases the CHILD nevus may occur in a more or less bilateral distribution. In 1997 Fink-Puches et al described a case of CHILD nevus with an almost symmetric arrangement. To test the correctness of the diagnosis, we now examined blood lymphocytes of this patient by single-strand conformation analysis and genomic sequencing. We identified a novel missense mutation in NSDHL that potentially may impair protein function. We conclude that a diagnosis of CHILD syndrome can be based on clinical features such as the highly characteristic morphology of the CHILD nevus. A symmetric distribution of this nevus can exceptionally be seen in patients with CHILD syndrome, and this bilateral involvement should not mislead the clinician to any other diagnosis. Apparently, the effect of random X-inactivation is responsible for different patterns of cutaneous involvement in female carriers of NSDHL mutations.

A giant verruciform xanthoma

BACKGROUND

Verruciform xanthoma (VX) is a rare, benign neoplasm arising predominantly in the oral cavity, but it has been reported to occur on the genital skin and mucosa as well. VX has also been described in association with epidermal nevi and squamous cell carcinoma. Because of the clinical and histologic similarities between VX and condyloma acuminata, and a recent report of HPV 6 in association with VX, we investigated the role of human papilloma virus (HPV) in the development of this entity.

METHODS

In situ hybridization and a nested PCR approach utilizing degenerate primers were utilized to establish whether HPV infection could be playing a role in the development of the VX.

RESULTS

In situ hybridization failed to identify HPV DNA. The highly sensitive nested PCR approach also failed to detect HPV DNA.

CONCLUSIONS

The failure to detect HPV DNA, even by very sensitive methods, provides strong evidence that our case of VX is not an HPV-induced lesion. A review of other possible etiologies, including alternative infectious agents and genetic associations, are discussed.