Clinical and molecular investigation of Buschke-Fischer-Brauer in consanguineous Tunisian families.

BACKGROUND: Punctate palmoplantar keratoderma type I (PPPK-BFB), also called Buschke-Fischer-Brauer disease (MIM 148600) is a rare autosomal dominant disorder of keratinization, characterized by multiple hyperkeratotic lesions on the palms and soles. Recently, PPPK-BFB has been shown to be associated with mutations in the AAGAB gene in several families of European, African, Canadian and Asian origins. OBJECTIVE: To characterize the clinical and genetic features of PPPK-BFB in a broad group of Tunisian patients. METHODS: Epidemiological and clinical data were collected from 18 PPPK-BFB patients belonging to eight Tunisian families. We carried out mutational and structural analysis for families not previously investigated. RESULTS: Sequencing of the remaining families identified a total of three different mutations in AAGAB gene: one founder mutation (c.348_349delAG, p.R116Sfs*1) specific to the inbred Tunisian population, one recurrent mutation and (c.370C>T, p.R124*) one novel variant (c.430C>G, p.E144K). This novel mutation, involving a conserved amino acid, is predicted to be probably damaging to the p34 protein function. Assessment of the phenotypic presentation of this group of Tunisian patients was marked by variable severity and varying age at onset with a possible presence of anticipation noted in five out of eight families (62.5%). There is no apparent genotype-phenotype correlation. Despite the high degree of inbreeding, no homozygous individuals for AAGAB mutations were observed. Homozygous carriers in AAGAB gene are likely non-viable. CONCLUSION: This study contributes to further characterize PPPK-BFB in consanguineous families and to extend the mutational spectrum of AAGAB gene in the Tunisian population.

Comorbidity in the Tunisian population.

Genetic diseases in the Tunisian population represent a real problem of public health as their spectrum encompasses more than 400 disorders. Their frequency and distribution in the country have been influenced by demographic, economic and social features especially consanguinity. In this article, we report on genetic disease association referred to as comorbidity and discuss factors influencing their expressivity. Seventy-five disease associations have been reported among Tunisian families. This comorbidity could be individual or familial. In 39 comorbid associations, consanguinity was noted. Twenty-one founder and 11 private mutations are the cause of 34 primary diseases and 13 of associated diseases. As the information dealing with this phenomenon is fragmented, we proposed to centralize it in this report in order to draw both clinicians' and researcher's attention on the occurrence of such disease associations in inbred populations as it makes genetic counseling and prenatal diagnosis challenging even when mutations are known.

Hailey-Hailey disease in Tunisia.

SUMMARY BACKGROUND: Most of the published reports on Hailey-Hailey disease (HHD) come from European and Asian countries. We report here the clinical and genetic investigation of 20 patients affected with HHD in Tunisia. METHODS: Affected individuals from three large teaching hospitals in Tunis were recruited for the study over a 25-year period. Nine patients were identified through the active files and examined together with their family members that were visited in their respective regions. We have clinically examined in total 65 individuals and then identified 11 new cases. Patients were included on the basis of evocative skin lesions, biopsy proven HHD and negative immunofluorescence. Investigations to rule out fungal, bacterial and viral infections were done according to clinical symptoms. RESULTS: Twenty patients (12 males and 8 females) from 8 families were included in the present study with more than 55% that were undiagnosed before this investigation. Four patients had mild disease, eight had moderate disease and another eight had severe disease, among whom seven were females. Parental consanguinity was found in 7 cases out of 20 cases (35%). The neck region was first affected in half (4/8) of the male patients. Groins were first affected in 42% (5/12) of the female patients. Depression complicated the course of the disease in two female patients with severe HHD. We report an original association of supernumerary nipples with HHD in two sisters from the north of Tunisia. In 10 patients, the disease has become less troublesome with aging. CONCLUSION: HHD is underestimated. Physicians must be aware of this disease in case of resistant intertriginous dermatosis especially with a positive family history as nine out of 20 patients were misdiagnosed.

Histological characterization of Darier's disease in Tunisian families.

BACKGROUND: Darier's disease (OMIM 124200) is an autosomal-dominant skin disorder characterized by warty papules and plaques in seborreheic areas, palmo-plantar pits and distinctive nail abnormalities. The disease has complete penetrance in adults and variable expressivity. It is caused by mutations in the ATP2A2 gene, which encodes the sarco/endoplasmic reticulum Ca(2+) ATPase type 2 isoform (SERCA2). OBJECTIVE: We report histological investigations of six unrelated Tunisian families including 15 affected individuals with Darier's disease mutations. RESULTS: The typical histological features of Darier's disease have been observed in the 15 patients. Variable histological features have been observed among Tunisian patients ranging from mild to moderate lesions of Darier's disease. A significant correlation has been observed between the clinical presentation of the Darier's disease (mild or moderate) and the intensity of the histological features. Isolated acral form of Darier's disease was seen in one case. Two distinct original associations have been observed: Darier's disease/pemphigus vulgaris in one patient and Darier's disease/ichtyosis in the other patient. CONCLUSION: Our findings confirmed the clinical heterogeneity of Darier's disease on the basis of histological study. The intensity of the histological features could be closely correlated to the severity of Darier's disease clinical presentation.

Supernumerary nipples in association with Hailey-Hailey disease in a Tunisian family.

Supernumerary nipples (SNs) or polythelia are developmental abnormalities of breast tissue. They are located along the embryonic mammary lines. Polythelia usually occurs as a sporadic abnormality, although familial aggregation has been occasionally reported. Hailey-Hailey disease is a rare autosomal genodermatosis characterized by disturbed keratinocyte adhesion. These cutaneous disorders have been described in correlation with many other abnormalities. We report here the association of Hailey-Hailey disease and supernumerary nipples in a Northern Tunisian family. To our knowledge, this is the first report of such a clinical association.

Mutation spectrum of glycogen storage disease type Ia in Tunisia: implication for molecular diagnosis.

Glycogen storage disease type Ia (GSD Ia; OMIM 232200) is an autosomal recessive disorder of glycogen metabolism caused by a deficiency of the microsomal glucose-6-phosphatase (G6Pase). It is characterized by short stature, hepatomegaly, hypoglycaemia, hyperuricaemia, and lactic acidaemia. Various mutations have been reported in the G6Pase gene (G6PC). In order to determine the mutation spectrum in Tunisia, we performed mutation analysis in 22 Tunisian type I glycogen storage disease (GSD I) patients belonging to 18 unrelated families. All patients were clinically classified as GSD Ia. The R83C mutation was found to be the major cause of GSD Ia, accounting for 24 of 36 mutant alleles (66.6%), The R170Q mutation was the second most frequent mutation; it accounts for 10 of 36 mutant alleles (27.7%). The R83C and R170Q mutations could be rapidly detected by PCR/RFLP. Since the majority of Tunisian patients carried R83C and/or R170Q mutations, we propose direct screening of these mutations as a rapid, valuable and noninvasive tool for diagnosis of GSD Ia in Tunisian as well as in Northern African populations.

Clinical and mutational investigations of tyrosinemia type II in Northern Tunisia: identification and structural characterization of two novel TAT mutations.

Tyrosinemia type II or Richner-Hanhart Syndrome (RHS) is an autosomal recessive disorder characterized by keratitis, palmoplantar keratosis, mental retardation, and elevated blood tyrosine levels. The disease is due to a deficiency of hepatic cytosolic tyrosine aminotransferase (TATc), an enzyme involved in the tyrosine catabolic pathway. Because of the high rate of consanguinity this disorder seems to be relatively common among the Arab and Mediterranean populations. RHS is characterized by inter and intrafamilial phenotypic variability. A large spectrum of mutations within TATc gene has been shown to be responsible for RHS. In the present study, we report the clinical features and the molecular investigation of RHS in three unrelated consanguineous Tunisian families including 7 patients with confirmed biochemical diagnosis of tyrosinemia type II. Mutation analyses were performed and two novel missense mutations were identified (C151Y) and (L273P) within exon 5 and exon 8, respectively. The 3D-structural characterization of these mutations provides evidence of defective folding of the mutant proteins, and likely alteration of the enzymatic activity. Phenotype variability was observed even among individuals sharing the same pathogenic mutation.

A novel missense mutation in the gene encoding SLURP-1 in patients with Mal de Meleda from northern Tunisia.

BACKGROUND: Mal de Meleda (MDM) is a rare autosomal recessive skin disorder which belongs to the clinically and genetically heterogeneous group of palmoplantar keratodermas (PPK). Clinically, MDM is characterized by erythema and hyperkeratosis of the palms and soles with sharp demarcation that appears soon after birth and progressively extends to the dorsal surface of the hands and feet. OBJECTIVES: Except for the molecular study reported in Algerian families, MDM has not yet been investigated in the Maghrebian population, characterized by its heterogeneous ethnic background and a high rate of consanguinity. In this study we report genetic and molecular investigations of eight unrelated consanguineous Tunisian families including 17 affected individuals. METHODS: Eight large consanguineous MDM families who originated from cities of northern Tunisia, with a total of 17 patients and 22 unaffected family members were investigated. Families were genotyped with the following microsatellite markers: CNG003, D8S1751 and D8S1836. Mutation analyses were performed in affected patients, in both parents and in unaffected individuals. Linkage analysis was also performed. RESULTS: All the clinical features of MDM were constantly present. Nevertheless variable severity was noted among patients. Histological details were recorded. The haplotype analysis of markers CNG003, D8S1751 and D8S1836 revealed that all affected offspring were homozygous by descent for the three polymorphic markers. The maximum lod score value, 3.22, confirmed the evidence for linkage to the ARS gene. Three haplotypes were observed, and the findings suggest that at least three different mutations within the ARS gene segregate with these haplotypes. Three different mutations were identified, the 82delT mutation previously described and two novel missense mutations. CONCLUSIONS: The results suggest that the ARS gene is likely to be responsible for MDM in the eight Tunisian families. The clinical variability in the expression of PPK in MDM Tunisian patients might be accounted for by the intervention of modifier genes influencing the MDM phenotype.