Molecular analysis of a series of Israeli families with Comèl-Netherton syndrome.

BACKGROUND: Comèl-Netherton syndrome is a rare congenital autosomal recessive disorder characterized by congenital ichthyosis, hair shaft abnormalities and atopic diathesis. It is caused by mutations in SPINK5, which encodes the serine protease inhibitor LEKTI. OBJECTIVES: To delineate the spectrum of mutations carried by a series of Israeli patients in an attempt to establish an effective diagnostic strategy for this disease in Israel. METHODS: Mutations were identified by direct sequencing of the entire coding sequence of SPINK5 and confirmed using polymerase chain reaction-restriction fragment length polymorphism. RESULTS: Three mutations were identified in seven families, of which two were novel. All mutations were predicted to result in premature termination of protein translation. CONCLUSIONS: This report presents the first case series of patients affected with Comèl-Netherton syndrome in Israel and suggests that some mutations reoccur in a substantial portion of cases in our country, a fact that should be taken into consideration when designing molecular analysis in new cases.

Human amnion membrane as a substrate for the detection of autoantibodies in pemphigus vulgaris and bullous pemphigoid.

BACKGROUND: Human amnion membrane (HAM) was suggested to be a superior antigenic substrate for immunoblotting in detecting autoantibodies of autoimmune bullous skin diseases. OBJECTIVES: To determine the properties of HAM as an antigenic substrate for the detection of autoantibodies in pemphigus vulgaris and bullous pemphigoid. METHODS: Immunomapping and tandem liquid chromatography mass spectrometry were used to delineate the antigenic structure of HAM. Immunoblotting and indirect immunofluorescence were used to study the diagnostic utility of HAM in 25 pemphigus patients, 41 pemphigoid patients, and 36 controls, and the results were compared to those of indirect immunofluorescence on monkey esophagus, immunoblotting using normal human skin, and enzyme-linked immunosorbent assay. RESULTS: Immunomapping demonstrated the presence of all the antigens known to be targeted in autoimmune bullous skin diseases, in both normal human skin and HAM, except for the absence of BP230, and low threshold levels of Dsg1, Dsg3 and Dsc3 in HAM. HAM indirect immunofluorescence demonstrated anti-basement membrane zone antibodies in 48.7% of the pemphigoid patients, and anti-intercellular space antibodies in 72.0% of the pemphigus patients. HAM immunoblotting did not demonstrate anti-BP230 antibodies, but detected anti-BP180 antibodies in 53.7% of the pemphigoid patients. It did not demonstrate anti-Dsg1 and/ or anti-Dsg3 antibodies in any of the pemphigus patients. These results were inferior to those of ELISA and monkey esophagus indirect immunofluorescence. CONCLUSIONS: Compared to other studied methods, HAM does not offer advantages in detecting autoantibodies in bullous pemphigoid and pemphigus vulgaris.

The sound of silence: autosomal recessive congenital ichthyosis caused by a synonymous mutation in ABCA12.

Autosomal recessive congenital ichthyosis refers to a heterogeneous group of cornification disorders of major impact on patients' life. The disease has been linked so far to mutations in 8 distinct genes. We report a consanguineous family of Arab Muslim origin with several members displaying a severe form of congenital ichthyosiform erythroderma. Using a panel of polymorphic microsatellite markers, we identified a region of homozygosity shared by all patients on 2q34, in a region harbouring the ABCA12 gene. Direct sequencing of genomic DNA derived from a patient failed to reveal any obviously pathogenic change in the coding sequence of this gene. In contrast, cDNA sequence analysis revealed the existence of a 163-bp-long deletion in exon 24, thus pointing to a splicing defect. Careful reanalysis of the genomic DNA sequence revealed apart from several known single-nucleotide polymorphisms, a hitherto unreported homozygous synonymous mutation in exon 24 (c.3456G>A; p.S1152S), which was found to lead to the formation of a novel splicing acceptor site. Synonymous mutations have been shown to uncommonly cause inherited disorders in humans. Here, we present the first example of a congenital form of ichthyosis resulting from such a genetic defect.

Mutations in GALNT3, encoding a protein involved in O-linked glycosylation, cause familial tumoral calcinosis.

Familial tumoral calcinosis (FTC; OMIM 211900) is a severe autosomal recessive metabolic disorder that manifests with hyperphosphatemia and massive calcium deposits in the skin and subcutaneous tissues. Using linkage analysis, we mapped the gene underlying FTC to 2q24-q31. This region includes the gene GALNT3, which encodes a glycosyltransferase responsible for initiating mucin-type O-glycosylation. Sequence analysis of GALNT3 identified biallelic deleterious mutations in all individuals with FTC, suggesting that defective post-translational modification underlies the disease.

Acrokeratosis verruciformis of Hopf showing P602L mutation in ATP2A2 and overlapping histopathological features with Darier disease.

The relationship between acrokeratosis verruciformis (AKV) of Hopf and Darier disease (DD) has been debated for several decades. Both diseases are now thought to result from mutations in the same gene, that is, the ATP2A2 gene encoding the sarco (endo) plasmic reticulum Ca ATPase2 pump (SERCA2), although their histopathological features are different. We sought to detect possible overlapping histopathological features between AKV and DD. Fourteen members of a family affected by AKV were analyzed for the underlying molecular genetic derangement, and 3 cases were studied histopathologically using multiple step sections. A heterozygous P602L mutation in ATP2A2 was identified as the underlying cause in this family. This mutation and a heterozygous A698V were previously described in AKV. Both mutations were not among the 162 mutations in ATP2A2, which were reported to date in DD. The histopathological study demonstrated in several consecutive step sections of 2 of the 3 studied cases, foci of small suprabasal clefts with acantholytic keratinocytes, some of which were mildly dyskeratotic. These focal features were reminiscent of the basic histopathological characteristics of DD. These shared histopathological features of AKV with DD suggest that AKV and DD are allelic disorders with variable expression of the same disease, although identical mutations in ATP2A2 in AKV and DD were not reported to date.

SERKAL syndrome: an autosomal-recessive disorder caused by a loss-of-function mutation in WNT4.

The WNT-signaling pathway plays a major role during mammalian embryogenesis. We report a novel autosomal-recessive syndrome that consists of female to male sex reversal and renal, adrenal, and lung dysgenesis and is associated with additional developmental defects. Using a candidate-gene approach, we identified a disease-causing homozygous missense mutation in the human WNT4 gene. The mutation was found to result in markedly reduced WNT4 mRNA levels in vivo and in vitro and to downregulate WNT4-dependent inhibition of beta-catenin degradation. Taken together with previous observations in animal models, the present data attribute a pivotal role to WNT4 signaling during organogenesis in humans.

Alopecia, neurological defects, and endocrinopathy syndrome caused by decreased expression of RBM28, a nucleolar protein associated with ribosome biogenesis.

Single-gene disorders offer unique opportunities to shed light upon fundamental physiological processes in humans. We investigated an autosomal-recessive phenotype characterized by alopecia, progressive neurological defects, and endocrinopathy (ANE syndrome). By using homozygosity mapping and candidate-gene analysis, we identified a loss-of-function mutation in RBM28, encoding a nucleolar protein. RBM28 yeast ortholog, Nop4p, was previously found to regulate ribosome biogenesis. Accordingly, electron microscopy revealed marked ribosome depletion and structural abnormalities of the rough endoplasmic reticulum in patient cells, ascribing ANE syndrome to the restricted group of inherited disorders associated with ribosomal dysfunction.

A case of H syndrome showing immunophenotye similarities to Rosai-Dorfman disease.

H syndrome (OMIM 612391) is a recently described autosomal recessive genodermatosis characterized by indurated, hyperpigmented, and hypertrichotic skin and systemic manifestations including hepatosplenomegaly, cardiac anomalies, hearing loss, hypogonadism, low height, hypertriglyceridemia, hallux valgus, and flexion contractures. H syndrome results from mutations in the SLC29A3 gene, which encodes the human equilibrative nucleoside transporter hENT3. The cutaneous histopathology is characterized by a striking mononuclear cell infiltrate in the dermis consisting of CD68+ monocyte-derived cells and CD34+ and factor XIIIa+ dendrocytes. We describe a case of H syndrome in which the infiltrating mononuclear cells were CD68+, CD163+, S-100+, and CD1a-, thus simulating the immunophenotype observed in Rosai-Dorfman disease (RDD). The immunostaining for CD21, fascin, and CD34 were negative, and there were also many factor XIIIa+ dendrocytes interspersed within the dense mononuclear cell infiltrate. Recent findings of biallelic mutations in SLC29A3 in 2 families reported to have familial RDD and in a kindred with Faisalabad histiocytosis (OMIM 602782), which is an autosomal inherited form of histiocytosis with similarities to RDD, may explain the RDD-like immunophenotype in our H syndrome case.

Disadhesion of epidermal keratinocytes: a histologic clue to palmoplantar keratodermas caused by DSG1 mutations.

BACKGROUND: Recent developments in molecular genetics may lead to re-examination of the histopathology of inherited palmoplantar keratodermas (PPKs) based on more precise groupings of the various entities and syndromes. OBJECTIVE: We sought to characterize the histopathological findings in PPKs associated with mutations in DSG1, which encodes desmoglein 1. METHODS: We studied the histopathology of 3 cases of keratosis palmoplantaris striata type I and one case of diffuse PPK, all associated with autosomal-dominant mutations in DSG1. Our cases for comparison included 4 cases with Mal de Meleda PPK associated with autosomal-recessive SLURP1 mutations, one case with pachyonychia congenita type II PPK associated with an autosomal-dominant KRT17 mutation, and one case with focal PPK associated with an autosomal-dominant KRT16 mutation. RESULTS: The distinguishing histopathological features of the 3 keratosis palmoplantaris striata type I cases and the diffuse PPK case associated with DSG1 mutation were: varying degrees of widening of the intercellular spaces and partial disadhesion of keratinocytes in the mid and upper epidermal spinous cell layers, often extending to the granular cell layer. These findings, which are associated with haploinsufficiency of desmoglein 1, were not observed in any of the other 6 PPK cases. Mild perinuclear eosinophilic condensations and cytoplasmic vacuolizations were observed in the spinous cell layer keratinocytes of the pachyonychia congenita type II PPK and the nonspecified focal PPK cases. LIMITATIONS: There were a limited number of patients and control patients with hereditary PPKs. CONCLUSION: Widening of the intercellular spaces and disadhesion of epidermal keratinocytes may serve as a histologic clue to PPKs caused by DSG1 mutations.

Buschke-Ollendorff syndrome in a three-generation family: influence of a novel LEMD3 mutation to tropoelastin expression.

Buschke-Ollendorff syndrome refers to the concomitant occurrence of connective tissue nevi, composed of elastic fibers in most cases, with osteopoikilosis. This autosomal dominant inherited disorder is caused by mutations in the gene LEMD3 on chromosome 12q14, which induces a rather heterogeneous clinical phenotype. Here, we report on the most proximal germline mutation found to date in the LEMD3 gene, p.Val94fs, in a three-generation Swiss family. Quantitative RNA analyses in affected and non-affected skin tissue from the proband demonstrate a comparable nonsense-mediated decay of mutant LEMD3 mRNA in both tissues; however, different levels of tropoelastin expression suggest that additional factors are involved in the development of the cutaneous lesions.

ADULT syndrome caused by a mutation previously associated with EEC syndrome.

Acro-Dermato-Ungual-Lacrimal-Tooth (ADULT) syndrome is a rare autosomal dominant syndrome characterized by ectrodactyly or syndactyly, excessive freckling and dry skin, dysplastic nails, lacrimal duct atresia, primary hypodontia and early loss of permanent teeth. ADULT syndrome is one of five such syndromes that result from mutations in TP63, encoding the transcription factor p63. Until now, only four families and three individuals with ADULT syndrome have been reported in the English literature. We present a 14-year-old female patient with ADULT syndrome and discuss phenotype-genotype correlations in the p63 syndromes.

Newly discovered mutations in the GALNT3 gene causing autosomal recessive hyperostosis-hyperphosphatemia syndrome.

BACKGROUND AND PURPOSE: Periosteal new bone formation and cortical hyperostosis often suggest an initial diagnosis of bone malignancy or osteomyelitis. In the present study, we investigated the cause of persistent bone hyperostosis in the offspring of two consanguineous parents. METHODS: Clinical assessment, imaging, and direct sequencing were used to elucidate the etiology of the condition seen in the patient. RESULTS: Radiological examination revealed periosteal reaction, diaphysitis, and cortical hyperostosis, suggesting osteomyelitis or a bone neoplasm. The clinical and radiological features were also reminiscent of hyperostosis with hyperphosphatemia (HHS), a rare autosomal recessive disease manifesting with recurrent, transient, and painful swelling of the long bones. The identification of two novel heterozygous pathogenic mutations in the GALNT3 gene confirmed a diagnosis of HHS. INTERPRETATION: Molecular analysis represents an invaluable tool in the differential diagnosis of persistent cortical hyperostosis.

The histopathology and phenotypic variability in H syndrome.

Skin biopsy may be helpful in the diagnosis of H syndrome. A triad of dermal fibrosis, lymphocytic aggregates, and numerous CD68+, CD163+, S100-positive, and CD1a-negative dermal histiocytes is characteristic.

Identification of mutations in the human hairless gene in two new families with congenital atrichia.

Congenital atrichia (AUC) is a form of isolated alopecia with an autosomal recessive mode of inheritance. Patients are born with normal hair but this is shed almost completely during the first weeks or months of life and never regrows. In many families the development of papular lesions is noted as an additional phenotypic feature, which defines a related phenotype designated as atrichia with papular lesions (APL). Using positional cloning strategies and the molecular findings in hairless recessive (hr/hr) mice, an animal model for AUC, mutations in the human hairless gene (HR) have been identified as a cause of AUC and APL. To date, more than 20 different mutations of the HR gene have been reported in AUC and APL including different mutation types scattered over the entire HR gene length. In this report, we describe two families of Saudi Arabian and Jewish Iranian origin comprising a number of individuals with clinical features suggestive of AUC. We therefore hypothesized that affected members may carry mutations in the HR gene. After sequencing the complete coding region of the HR gene in the Saudi Arabian family, we identified a homozygous insertion of a G (c.2661dupG; p.Thr888DfsX38) in exon 12, resulting in a premature stop codon. In a Jewish Iranian patient, we identified a homozygous splice site mutation c.1557-1G > T in intron 4. The latter mutation has been previously reported in a compound heterozygous state. In the present report, we describe the second exonic insertion mutation in the human HR gene and the first mutation in exon 12. Our study emphasizes the importance of sequencing the complete coding sequence and exon/intron junctions in the molecular diagnostics of AUC and APL.

Molecular epidemiology of hereditary epidermolysis bullosa in a Middle Eastern population.

Epidermolysis bullosa (EB) encompasses a large group of inherited blistering skin disorders caused by mutations in at least 10 genes. Numerous studies, mainly performed in European and US families with EB, have revealed a number of characteristic epidemiological and genetic features, which form the basis for current diagnostic and counseling strategies. However, little is currently known about the molecular epidemiology of EB in Middle East populations. In the present study, we assessed 55 EB families for pathogenic sequence alterations in the 10 genes known to be associated with EB. Our results show unique EB subtype distribution and patterns of inheritance in our cohort. We also failed to detect recurrent mutations frequently encountered in Europe and the US, and did not consistently observe genotype-phenotype correlations formerly established in Western populations. Thus, the molecular epidemiology of EB in the Middle East is significantly different from that previously delineated in Europe and the US. Our data raise the possibility that similar differences may also be found in other genetically heterogeneous groups of disorders, and indicate the need for population-specific diagnostic and management approaches.

Homozygosity mapping as a screening tool for the molecular diagnosis of hereditary skin diseases in consanguineous populations.

BACKGROUND: The routine diagnosis of genodermatoses is significantly complicated by the fact that in this group of disorders, clinical manifestations may result from mutations in unrelated genes (genetic heterogeneity) and mutations in the same gene often lead to dissimilar clinical signs (phenotypic heterogeneity). METHODS: In this study, we applied the principles of homozygosity mapping as a screening method before formal mutational analysis in an attempt to facilitate the molecular diagnosis of genodermatoses in consanguineous families. The method was evaluated in a retrospective fashion in 4 families previously assessed with junctional epidermolysis bullosa and in a prospective manner in 11 families with congenital recessive ichthyosis. RESULTS: The method was found to be efficient in directing the molecular analysis to one of the 4 genes commonly involved in the pathogenesis of junctional epidermolysis bullosa or in identifying cases of congenital recessive ichthyosis caused by mutations in TGM1. We found that this diagnostic strategy results in a 5-fold decrease in the cost of mutation analysis. LIMITATIONS: The proposed diagnostic strategy is applicable to consanguineous families only and, therefore, cannot be used in outbred populations. CONCLUSION: Our results indicate that homozygosity mapping may serve as a useful adjunct in the molecular diagnosis of junctional epidermolysis bullosa or congenital recessive ichthyosis in inbred populations. This study emphasizes the usefulness in human genetics of diagnostic strategies tailored to the demographic features of target populations.

Identification of a novel locus associated with congenital recessive ichthyosis on 12p11.2-q13.

Congenital recessive ichthyoses represent a vast and markedly heterogeneous group of diseases that have been mapped to at least seven distinct chromosomal loci. In this study, we ascertained two consanguineous families presenting with congenital ichthyosis. Using homozygosity mapping, we identified a 6.5 cM homozygous region on 12p11.2-q13 shared by all affected individuals. Multipoint logarithm of odds ratio (LOD) score analysis placed the new locus between markers D12S345 and D12S390 with a maximum LOD score of 4.79 at marker CH12SSR13. This region harbors PPHLN1, encoding periphilin 1, a protein involved in the cornification process. No deleterious mutations were identified within the coding region of this gene, suggesting the existence of another gene associated with epidermal differentiation on 12p11.2-q13.

Homozygous splice site mutations in PKP1 result in loss of epidermal plakophilin 1 expression and underlie ectodermal dysplasia/skin fragility syndrome in two consanguineous families.

During the last years, a growing number of inherited skin disorders have been recognized to be caused by abnormal function of desmosomal proteins. In the present study, we describe the first female individuals affected with the ectodermal dysplasia/skin fragility syndrome (MIM604536), a rare autosomal recessive disease due to mutations in the PKP1 gene encoding plakophilin 1, a critical component of desmosomal plaque. One patient was shown to carry a homozygous splice site mutation in intron 4. The second patient displayed a homozygous recurrent mutation affecting the acceptor splice site of intron 1. Both mutations were associated with intraepidermal separation, widening of intercellular spaces, and abnormal desmosome ultrastructure, and were found to result in the absence of immunoreactive plakophilin 1 in the epidermis of the affected individuals. These two cases emphasize the role of molecular genetics in the assessment of congenital blistering in newborns and illustrate the importance of proper desmosomal activity for normal epidermis development and function.