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Background Bazex–Dupré–Christol syndrome (BDCS; MIM301845) is a rare X-linked dominant genodermatosis characterized by follicular atrophoderma, congenital hypotrichosis and multiple basal cell carcinomas (BCCs). Previous studies have linked BDCS to an 11·4-Mb interval on chromosome Xq25-q27.1. However, the genetic mechanism of BDCS remains an open question. Objectives To investigate the genetic aetiology and molecular mechanisms underlying BDCS. Methods We ascertained multiple individuals from eight unrelated families affected with BDCS (F1–F8). Whole-exome (F1 and F2) and genome sequencing (F3) were performed to identify putative disease-causing variants within the linkage region. Array comparative genomic hybridization and quantitative polymerase chain reaction (PCR) were used to explore copy number variations, followed by long-range gap PCR and Sanger sequencing to amplify the duplication junctions and to define the head–tail junctions. Hi-C was performed on dermal fibroblasts from two affected individuals with BDCS and one control. Public datasets and tools were used to identify regulatory elements and transcription factor binding sites within the minimal duplicated region. Immunofluorescence was performed in hair follicles, BCCs and trichoepitheliomas from patients with BDCS and sporadic BCCs. The ACTRT1 variant c.547dup (p.Met183Asnfs*17), previously proposed to cause BDCS, was evaluated with t allele frequency calculator. Results In eight families with BDCS, we identified overlapping 18–135-kb duplications (six inherited and two de novo) at Xq26.1, flanked by ARHGAP36 and IGSF1. Hi-C showed that the duplications did not affect the topologically associated domain, but may alter the interactions between flanking genes and putative enhancers located in the minimal duplicated region. We detected ARHGAP36 expression near the control hair follicular stem cell compartment, and found increased ARHGAP36 levels in hair follicles in telogen, in BCCs and in trichoepitheliomas from patients with BDCS. ARHGAP36 was also detected in sporadic BCCs from individuals without BDCS. Our modelling showed the predicted maximum tolerated minor allele frequency of ACTRT1 variants in control populations to be orders of magnitude higher than expected for a high-penetrant ultra-rare disorder, suggesting loss of function of ACTRT1 variants to be an unlikely cause for BDCS. Conclusions Noncoding Xq26.1 duplications cause BDCS. The BDCS duplications most likely lead to dysregulation of ARHGAP36. ARHGAP36 is a potential therapeutic target for both inherited and sporadic BCCs. What is already known about this topic? Bazex–Dupré–Christol syndrome (BDCS) is a rare X-linked basal cell carcinoma susceptibility syndrome linked to an 11·4-Mb interval on chromosome Xq25-q27.1.Loss-of-function variants in ACTRT1 and its regulatory elements were suggested to cause BDCS. What does this study add? BDCS is caused by small tandem noncoding intergenic duplications at chromosome Xq26.1.The Xq26.1 BDCS duplications likely dysregulate ARHGAP36, the flanking centromeric gene.ACTRT1 loss-of-function variants are unlikely to cause BDCS. What is the translational message? This study provides the basis for accurate genetic testing for BDCS, which will aid precise diagnosis and appropriate surveillance and clinical management.ARHGAP36 may be a novel therapeutic target for all forms of sporadic basal cell carcinomas.

Background Mutations in the ST14 gene, encoding the serine protease matriptase, have been associated with ichthyosis-hypotrichosis syndrome (IHS), a Mendelian disorder with skin and hair manifestations which include, in addition to ichthyosis and hypotrichosis, hypohidrosis and follicular atrophoderma. However, the understanding of the specific consequences of mutations in ST14 on the development of this syndrome is incomplete. Results Using a targeted next-generation sequencing array of 38 ichthyosis-associated genes on a large cohort of 180 ichthyosis patients from a primarily consanguineous background, a previously unreported homozygous p.Asp482Asn mutation in ST14 was identified in a patient with IHS. This mutation affects an essential site within a ligand-binding domain of matriptase. Comparison with previous reports of IHS allowed further delineation of the phenotype of IHS in correlation with mutations present in these patients. Histological and ultrastructural analysis of skin and hair identified novel features in this disorder. Conclusions This study correlates genotypic and phenotypic features of the rare disorder, IHS, expands the spectrum of pathology associated with the disorder, and provides clinical evidence of the importance of the Asp482 amino acid, previously shown to have an essential role in matriptase activation.

Actin-Related Protein-Testis1 (ARP-T1)/ ACTRT1 gene mutations cause the Bazex-Dupré-Christol Syndrome (BDCS) characterized by follicular atrophoderma, hypotrichosis and basal cell cancer. Here, we report an ARP-T1 interactome (PXD016557) involved in ciliogenesis, endosomal recycling and septin ring formation. Consequently, ARP-T1 localizes to the midbody during cytokinesis and the basal body of primary cilia in G0. Tissue samples from BDCS patients show reduced ciliary length with significant correlations of ARP-T1 expression levels, confirmed by ACTRT1 knock down. We report that BDCS is a novel ciliopathy and the first case of a skin cancer ciliopathy, where ARP-T1 plays a critical role to prevent pathogenesis.

Congenital ichthyosis encompasses a heterogeneous group of disorders of cornification. Isolated forms and syndromic ichthyosis can be differentiated. We have analyzed two consanguineous families from the United Arab Emirates and Turkey with an autosomal recessive syndrome of diffuse congenital ichthyosis, patchy follicular atrophoderma, generalized and diffuse nonscarring hypotrichosis, marked hypohidrosis, and woolly hair (OMIM 602400). By genome-wide analysis, we found a homozygous interval on chromosome 11q24–q25 and obtained a LOD score of 4.0 at D11S910. We identified a homozygous splice-site mutation in the Arab patients and a frame-shift deletion in the Turkish patient in the gene suppression of tumorigenicity-14 (ST14). The product of ST14, matriptase, is a type II transmembrane serine protease synthesized in most human epithelia. Two missense mutations in ST14 were recently described in patients with a phenotype of ichthyosis and hypotrichosis, indicating diverse activities of matriptase in the epidermis and hair follicles. Here we have further demonstrated the loss of matriptase in differentiated patient keratinocytes, reduced proteolytic activation of prostasin, and disturbed processing of profilaggrin. As filaggrin monomers play a pivotal role in epidermal barrier formation, these findings reveal the link between congenital disorders of keratinization and filaggrin processing in the human skin.

This paper suggests that there is probably a dominant, sex-linked type of chondrodysplasia punctata. Clinical data are reported for three girls with such a disorder. Two of their mothers showed a mild form of cicatricial alopecia. The pathognomonic dermatological findings in the children include erythematous skin changes and striated ichthyosiform hyperkeratosis during the first months of life. Later on, patterned ichthyosis, follicular atrophoderma, coarse, lusterless hair and cicatricial alopecia become evident. It is assumed that about one fourth of all cases with chondrodysplasia punctata reported in the literature belong to the dominant sex-linked type.

Bazex-Dupre-Christol syndrome is an X-linked dominantly inherited disorder characterized by congenital hypotrichosis, hypohidrosis, follicular atrophoderma, multiple milia and basal cell carcinomas. We present a girl and her family with this syndrome. Our patient, her 5 month old brother and her 17 year old brother had multiple milia and scalp and eyebrows hypotrichosis. Her 8 year old brother had multiple milia and follicular atrophoderma. Her mother had hypohidrosis and congenital scalp and eyebrows hypotrichosis, as well as a right paranasal lesion suggestive of basal cell carcinoma. We emphasize the importance of precise diagnosis and clinical follow up of these patients due to the possibility of developing basal cell carcinomas.

Bazex-Dupre-Christol syndrome (BDCS) is an X linked dominant disorder of the hair follicle characterised by follicular atrophoderma, multiple basal cell carcinomas, hypotrichosis, milia, and localised hypohidrosis. Follicular atrophoderma (FA) are follicular funnel shaped depressions, "ice pick marks", seen most commonly on the dorsum of the hands. We describe the first known Scottish family with this syndrome, five affected members spanning three generations. They have hypohidrosis confined to the face, coarse hair, dry skin, milia, and follicular atrophoderma. All the adults have a history of multiple basal cell carcinomas. None of them has any skeletal feature suggestive of Gorlin's syndrome. The clinical features, skin histology, and scanning electron microscopic (SEM) examination of the hair are described and illustrated. The features are compared with 15 previous reports of BDCS and four reports in which this is a possible diagnosis are also reviewed. BDCS should be considered as a differential diagnosis in patients with early onset or familial basal cell carcinomas.

Bazex-Dupré-Christol syndrome is an inherited condition with skin cancer predisposition characterized by follicular atrophoderma, hypotrichosis, and early onset of multiple basal cell carcinomas. Previous reports suggested an X-linked mode of inheritance. We therefore performed linkage analysis with microsatellite markers of the X chromosome in three families. We obtained evidence for X-linkage and regional assignment to Xq24-q27 of this syndrome (maximal lod score = 5.26 with a recombination fraction of 0% at the DXSl192 locus). This represents a first step towards the identification of a gene involved in hair follicle development and skin tumor formation.

A seven-year-old girl was born with red, scaly skin that later evolved into hypopigmentation and follicular atrophoderma in a widespread distribution that followed Blaschko lines. She also had patchy, scarring alopecia, left microphthalmia, bilateral cataracts, dysmorphic facies, short stature, hip dysplasia, and vertebral abnormalities. An elevated plasma 8(9)-cholestenol level confirmed the diagnosis of Conradi-Hunermann-Happle syndrome, which is caused by mutations in the emopamil binding protein (EBP) gene. This reports highlights the evolution of clinical findings over time in this X-linked dominant form of chondrodysplasia punctata.

Conradi-Hunermann-Happle syndrome, or X-linked dominant chondrodysplasia punctata, is a rare genetic disorder characterized by skeletal dysplasia, stippled epiphyses, cataracts, transient ichthyosis and atrophic residua in a mosaic pattern. Mutations in the gene encoding the emopamil-binding protein have been identified as an underlying cause. A 5-year-old girl presented for evaluation of ill-defined patches of cicatricial alopecia. In addition, subtle follicular atrophoderma, esotropia, craniofacial asymmetry and short stature were noted. Her history revealed widespread scaly erythema and eye surgery for congenital cataract in the first months of life. Diagnosis of Conradi-Hunermann-Happle syndrome was confirmed by plasma sterol analysis showing markedly elevated levels of 8(9)-cholestenol and 8-dehydrocholesterol and by detection of a missense mutation (c.307G>A; p.E103K) in the emopamil-binding protein gene. We suggest that plasma sterol analysis is a reliable method of establishing the diagnosis of Conradi-Hunermann-Happle syndrome, even in patients with less striking phenotypical changes beyond infancy.

A 6-year-old male child presented with progressive hypertrophy and discoloration of all 20 nails. Further evaluation revealed milia in bilateral concha and face, which were present since infancy. Other findings included atrophoderma over bilateral sides of lateral canthi of eyes and absent lower central incisors. Past medical and family history had remarkable findings such as natal teeth and similar nail changes in his elder sister. Similar nail changes, milia and focal plantar keratoderma were present in his father and elder sister. The patient's clinical presentation and history were compatible with pachyonychia congenita subtype 2.

Chodrodysplasia punctata is a very rare disease, and was first described by Conradi in 1914. Almost 200 cases have been reported in the world, and 33 cases in Japan.The essential feature of this condition is the presence of stippled foci of calcification within the hyaline cartilage in infancy. And this disease is frequently associated with multiple congenital abnormalities, as cataract, saddle nose, follicular atrophoderma, contractures of joints, dwarfing of the limbs, kyphoscoliosis, mental retardation, etc.Three cases of Conradi-Hunermann type of chondrodysplasia punctata, diagnosed in infancy, are presented. They were followed for about 10 years.

In 1943 Miescher (1) reported peculiar atrophic changes of the skin of body and scalp in a 7 year old Swiss girl. There were spots of atrophic alopecia on the scalp, and on the extremities and trunk irregular zones in which dimple-like depressions were found at the place of follicular orifices. The child was very small and had thoracic kyphoscoliosis, lumbar lordosis, luxation of the right hip, a considerably shortened right leg, and a moderately shortened left arm. Five years earlier, Burckhardt (2) has described the skeletal condition of the same child, then 2 years old, as chondrodystrophia foetalis calcarea. In the English speaking countries this disease is called chondrodystrophia calcificans congenita, chondro-osseous dystrophy with punctate epiphyseal dysplasia, or similar variations.