A novel large deletion in CCM1 gene in a Tunisian family.

Familial CCM is a rare entity associated with the mutation of three genes: CCM1 (KRIT1), CCM2 (MGC4607), and CCM3 (PDCD10). We report here the first description of a Tunisian familial CCMs composed of six members. The father and two daughters were affected and symptomatic. The two other kindred were healthy. Surgical treatment was performed in only one affected patient. Molecular analysis of KRIT1, MGC4607 and PDCD10 genes identified a large KRIT1 deletion of the first ten exons. To the best of our knowledge, this large deletion has never been reported before.

Xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is a form of general dermatosis characterised by photo-induced cutaneous-ocular impairment and by skin cancers. In addition to these signs, there may also be neurological involvement. This disease is related to a defect in genes within the nucleotide excision repair system for the first seven genetic groups (A-G), and to an abnormality in transcription groups for the eighth group (xeroderma pigmentosum variant - XPV). Cutaneous carcinomas are the most common types of cancer seen. They may begin in childhood. Multiple melanoma commonly occurs during the course of XP but given the frequency of spontaneous regression, the incidence is underestimated. The clinical appearance is characterised by polymorphous lesions with characteristic dyschromia and in most cases it is sufficient to establish the diagnosis. Investigation of unscheduled DNA synthesis (UDS) and cell survival following ultraviolet (UV) radiation were formerly considered the reference examination for laboratory diagnosis. However, these tests are now being replaced by new molecular biology techniques to screen for the genetic mutations characteristic of the disease. These techniques have proved extremely useful in identifying heterozygous patients and in antenatal diagnosis. Photoprotection is the key preventive measure: patients must avoid all exposure to the sun and to artificial sources of UV radiation. The therapeutic arsenal has recently been enriched by several modern therapeutic methods used to destroy cutaneous tumours such as imiquimod and photodynamic therapy (PDT). These approaches are valuable since they eliminate incipient tumours while sparing healthy skin. Surgery and cryosurgery are the most suitable methods for treating cutaneous tumours in children. Chemotherapy may be considered an alternative for the treatment of keratoacanthomas and squamous cell carcinomas (SCC). Cryosurgery may be combined with other therapeutic approaches to eliminate SCC of the lip. Management of these patients in reference centres, coupled with assistance from associations providing support for patients' families, has resulted in improved quality of therapy while slowing down disease progression.

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.

Retinal dystrophy and congenital glaucoma as major causes of vision loss in students attending two institutions for the visually disabled in Tunis city, Tunisia.

PURPOSE: To assess vision loss, identify affected anatomical sites, determine etiologies and potentially avoidable causes in students attending two institutions for the visually disabled in Tunis city. METHODS: A visit for a complete ophthalmological examination was performed. All students attending these schools were recruited in our study. The World Health Organisation Programme for the Prevention of Blindness (WHO/PBL) examination record for children was used. Data was analysed by the SPSS version 17 statistical software. RESULTS: A total of 172 students were recruited with mean age of 11.9±3.3 years (between 6 and 18 years). One hundred and thirty-seven (79.6%) were under 16 years. The sex-ratio was 1.17. Ninety students (52.3%) had low vision and eighty-two (47.7%) were blind. We reported retina (29%), whole globe (29%), globe appears normal (11%) and optic nerve (9.8%) as the common sites of ocular abnormalities. Retinal dystrophy (22.7%) and congenital glaucoma (22.7%) were the most reported ocular diseases. The main etiologies were hereditary (54.1%) and unknown (30.8%). Consanguinity was reported in 108 students (62.8%), and fifty-five students (32%) had a positive family history. Overall, 50.5% (87/172) of ocular diseases were potentially treatable or preventable. CONCLUSION: Retinal dystrophy and congenital glaucoma were the most common eye diseases. Heredity was the main etiology, and consanguinity was high. To decrease their incidence, awareness of the family members of the risks of consanguinous marriage and appropriate therapy for congenital glaucoma/cataract may significantly improve the child's visual prognosis.

Biotinidase deficiency: novel mutations in Algerian patients.

Biotinidase deficiency is an autosomal recessive disorder of biotin metabolism leading to varying degrees of neurologic and cutaneous symptoms when untreated. In the present study, we report the clinical features and the molecular investigation of biotinidase deficiency in four unrelated consanguineous Algerian families including five patients with profound biotinidase deficiency and one child characterized as partial biotinidase deficiency. Mutation analysis revealed three novel mutations, c.del631C and c.1557T>G within exon 4 and c.324-325insTA in exon 3. Since newborn screening is not available in Algeria, cascade screening in affected families would be very helpful to identify at risk individuals.

The experience of a Tunisian referral centre in prenatal diagnosis of Xeroderma pigmentosum.

AIMS: Xeroderma pigmentosum (XP, OMIM 278700-278780) is one of the most severe genodermatoses and is relatively frequent in Tunisia. In the absence of any therapy and to better manage the disease, we aimed to develop a molecular tool for DNA-based prenatal diagnosis. METHODS: Six consanguineous Tunisian XP families (4 XP-A and 2 XP-C) have benefited from a prenatal diagnosis. Screening for mutations was performed by direct sequencing, while maternal-foetal contamination was checked by genotyping. RESULTS: Among the 7 prenatal diagnoses, 4 foetuses were heterozygous for the screened mutation. Exclusion of contamination by maternal cells was checked. Mutations were detected at a homozygous state in the remaining cases, and the parents decided to terminate pregnancy. CONCLUSION: Our study illustrates the implementation of prenatal diagnosis for better health support of XP in Tunisia.

[Molecular diagnosis of Gaucher disease in Tunisia]. / Diagnostic moléculaire de la maladie de Gaucher en Tunisie.

Gaucher disease is a lysosomal storage disorder caused by a deficiency of the enzyme acid ß-glucosidase. In order to determine the mutation spectrum in Tunisia, we performed recurrent mutation screening in 30 Tunisian patients with Gaucher disease. Screening of recurrent mutation by PCR/RFLP and direct sequencing had shown that N370S was the most frequent mutation (22/50 mutant alleles, 44%), followed by L444P mutation, which is found in 16% (8/50 mutant alleles). The recombinant allele (RecNciI) represented 14%. Our findings revealed that the genotype N370S/RecNciI was mosst frequent in patients with childhood onset and it was associated with severe visceral involvement. The screening of these three mutations provided a simple tool for molecular diagnosis of Gaucher disease in Tunisian patients and allowed also genetic counselling for their family members.

A novel 22bp deletion in a Tunisian phenylketonuria family.

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by a deficiency of phenylalanine hydroxylase. To date, more than 530 mutations in the PAH gene have been reported. In Tunisia, this disease seems to be the result of point mutations, few studies have been published about molecular defects of PKU in our country. In this study, we report a novel deletion in exon 6 of two brothers in a Tunisian family after DHPLC analysis and sequencing of the exon 6 of the PAH gene.

[Creation and report of the Tunisian Fanconi Anemia Registry (TFAR)]. / Création et rapport du registre tunisien de l'anémie de Fanconi (TFAR).

INTRODUCTION: Fanconi anemia (FA) is a genetically and phenotypically heterogeneous inherited disease. Many groups have established FA registries. In Tunisia, in collaboration with the Tunisian Fanconi Anemia Study Group (TFASG), we set up the Tunisian Fanconi Anemia Registry (TFAR). PATIENTS AND METHODS: We contacted all hematology and pediatrics departments to include their FA patients diagnosed between January 1983 and December 2008. The registry is available on the TFASG web site (www.fanconi-tunisie.net). RESULTS: Sorting the files brought out 142 patients belonging to 118 families. The mean age at diagnosis was 11 years. There was consanguinity in 86%, malformative syndrome in 91%, and pancytopenia at diagnosis in 69%. Of 28 patients, 95% belonged to the FANCA group. Androgen treatment was given in 109 cases and genoidentical bone marrow transplantation (BMT) in 27 patients. The diagnosis of a myelodysplastic syndrome was retained in 4%, acute leukemia in 6%, and a solid tumor in 2%. The median overall survival time in all patients is 17 years 5 months; it is significantly better in patients having received allografts (p=0.01). CONCLUSION: FA seems frequent in Tunisia, which is in part explained by the high consanguinity and endogamy in this country. Hematologic impairment is still the most frequent revealing circumstance of the disease. It is often severe or moderate and requires androgen treatment or bone marrow transplantation. BMT should be proposed to all patients with an HLA-compatible donor.

Severe phenotypes in two Tunisian families with novel XPA mutations: evidence for a correlation between mutation location and disease severity.

Xeroderma pigmentosum (XP) is a rare disorder characterized by a high skin sun-sensitivity predisposing to skin cancers at an early age. Among Tunisian XP patients with an intermediate skin phenotype, 92% presented neurological abnormalities related to XPA gene deficiency. Clinical variability of the XP-A phenotype is associated with a mutational heterogeneity. In the present study, two Tunisian families with severe dermatological and neurological XP phenotypes were investigated in order to determine clinical characteristics and genetic basis. Two Tunisian families with four XP affected children were examined in the Dermatology Department. Clinical features showed severe presentation of the disease. Coding regions of the XPA gene were analysed by direct sequencing. Results showed the presence of a novel mutation, p.E111X, in three patients belonging to the same family and presenting a very severe phenotype i.e. development of skin lesions and neurological signs before 1 year age. For the other patient, we identified a nonsense mutation, p.R207X, already identified in a Palestinian XP-A patient. Identification of novel causing mutations in Tunisian XP-A patients shows the genetic and mutational heterogeneity of the disease in Tunisia. Despite a relatively homogenous mutational spectrum, mutational heterogeneity for rare cases is observed because of the high rate of consanguinity.

Homogénéité mutationnelle de la glycogénose de type Ia en Tunisie.

The glycogen storage disease type Ia (GSD Ia) is a rare inherited disorder, with autosomal recessive determinism. It is characterized by hepatomegaly, short stature and hypoglycemia with lactic acidemia. The confirmation of diagnosis is based on the enzymatic assay performed on liver biopsy. For Tunisians patients, this biochemical test is performed abroad. The aim of our study is the molecular characterization of GSD Ia in Tunisian patients and the development of a molecular diagnosis tool. Our study included 27 patients from 23 unrelated families, mutation analysis revealed that the R83C mutation is the most frequent (65%, 30/46 mutant alleles), followed by the R170Q mutation (30%, 14/46 mutant alleles). The homogeneity of mutation spectrum of GSD Ia in Tunisia allows the development of a cost effective and reliable tool for the confirmation of clinical diagnosis among suspected GSD Ia patients.

[Biochemical and molecular diagnosis of primary hyperoxaluria type 1: Tunisian study about 15 cases]. / Diagnostic biochimique et moléculaire de l'hyperoxalurie primaire de type 1: étude tunisienne à propos de 15 cas.

BACKGROUND: The primary type 1 hyperoxaluria (HP1) is the most frequent and severe form of the primary hyperoxaluriae. It is related to an enzymatic deficit in alanine glyoxylate aminotransferase (AGT). It is a recessive autosomic disease. Rare in Europe, it is responsible for 13% of the end stage renal failure in the Tunisian child. AIM: The aim of this work is to evaluate the biological and molecular examinations contributing with the early diagnosis and the follow-up of the HP1 patients and to test their response to pyridoxin. PATIENTS AND METHODS: A prospective study of 15 children who have oxaluria lower than 500 µmol/l and normal renal function is carried out. The cristalluria study, oxaluria and the glycolate-glycerate urinary ratio were carried out on all the patients. The so-called mutation maghrebean T853 (Ile244 Thr) was detected by direct sequencing of the exon 7 gene AGXT. The response to pyridoxin was tested among 13 patients. RESULTS: The oxaluria concentration was greater or equal to 1000 µmol/l in nine cases (60%) and ranging between 600 and 1000 µmol/l in the remaining cases. The oxaluria flow was significantly high depending on the age. The glycolaturia was high among eight patients (57%). In 61,5% of the cases, the most frequent crystalline species was whewellite (C1). The "maghrebin" mutation was identified in nine patients at the heterozygous state, showing 25% allelic frequency. The response to pyridoxin was observed in the 13 tested cases. CONCLUSION: The HP1 is frequent in our country from where the need for an early diagnosis. The use of simple biochemical tools such as the study of the cristalluria, the morphological analysis of stones and the oxaluria allow to direct the diagnosis towards a HP1, confirmed by the glycolaturia determination. The molecular biology is required in the atypical forms.

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.

Identification of a primarily neurological phenotypic expression of xeroderma pigmentosum complementation group A in a Tunisian family.

Xeroderma pigmentosum (XP) is a rare genodermatosis predisposing to skin cancers. The disease is classified into eight groups. Among them, XP group A (XP-A) is characterized by the presence of neurological abnormalities in addition to cutaneous symptoms. In the present study, we report a particular family with XP-A in which some members showed an atypical clinical presentation, i.e. unexplained neurological abnormalities with discrete skin manifestations. Molecular investigation allowed identification of a novel XPA mutation and complete phenotype-genotype correlation for this new phenotypic expression of XP-A.

Identification of two novel variants in PRKAG2 gene in Tunisian type 2 diabetic patients with family history of cardiovascular disease.

We report the identification of two novel polymorphisms in the PRKAG2 gene and preliminary association study between 5'-UTR and exon 1 polymorphisms with susceptibility to type 2 diabetes. No association with type 2 diabetes was identified. However, one of these newly identified polymorphisms (p.Ser20Ile) is likely associated with cardiac disease.