Molecular diagnosis of distal renal tubular acidosis in Tunisian patients: proposed algorithm for Northern Africa populations for the ATP6V1B1, ATP6V0A4 and SCL4A1 genes.

BACKGROUND: Primary distal renal tubular acidosis (dRTA) caused by mutations in the genes that codify for the H + -ATPase pump subunits is a heterogeneous disease with a poor phenotype-genotype correlation. Up to now, large cohorts of dRTA Tunisian patients have not been analyzed, and molecular defects may differ from those described in other ethnicities. We aim to identify molecular defects present in the ATP6V1B1, ATP6V0A4 and SLC4A1 genes in a Tunisian cohort, according to the following algorithm: first, ATP6V1B1 gene analysis in dRTA patients with sensorineural hearing loss (SNHL) or unknown hearing status. Afterwards, ATP6V0A4 gene study in dRTA patients with normal hearing, and in those without any structural mutation in the ATP6V1B1 gene despite presenting SNHL. Finally, analysis of the SLC4A1 gene in those patients with a negative result for the previous studies. METHODS: 25 children (19 boys) with dRTA from 20 families of Tunisian origin were studied. DNAs were extracted by the standard phenol/chloroform method. Molecular analysis was performed by PCR amplification and direct sequencing. RESULTS: In the index cases, ATP6V1B1 gene screening resulted in a mutation detection rate of 81.25%, which increased up to 95% after ATP6V0A4 gene analysis. Three ATP6V1B1 mutations were observed: one frameshift mutation (c.1155dupC; p.Ile386fs), in exon 12; a G to C single nucleotide substitution, on the acceptor splicing site (c.175-1G > C; p.?) in intron 2, and one novel missense mutation (c.1102G > A; p.Glu368Lys), in exon 11. We also report four mutations in the ATP6V0A4 gene: one single nucleotide deletion in exon 13 (c.1221delG; p.Met408Cysfs*10); the nonsense c.16C > T; p.Arg6*, in exon 3; and the missense changes c.1739 T > C; p.Met580Thr, in exon 17 and c.2035G > T; p.Asp679Tyr, in exon 19. CONCLUSION: Molecular diagnosis of ATP6V1B1 and ATP6V0A4 genes was performed in a large Tunisian cohort with dRTA. We identified three different ATP6V1B1 and four different ATP6V0A4 mutations in 25 Tunisian children. One of them, c.1102G > A; p.Glu368Lys in the ATP6V1B1 gene, had not previously been described. Among deaf since childhood patients, 75% had the ATP6V1B1 gene c.1155dupC mutation in homozygosis. Based on the results, we propose a new diagnostic strategy to facilitate the genetic testing in North Africans with dRTA and SNHL.

Contribution of laparoscopy in the abdominal tuberculosis diagnosis: retrospective study of about 11 cases.

OBJECTIVE: Abdominal tuberculosis is one of the most frequent extra-pulmonary localizations. Its diagnosis is difficult and may lead to a delayed prescription of specific treatment. This study is aimed at stressing the role of laparoscopy associated with a biopsy in the diagnostic confirmation of abdominal tuberculosis particularly in doubtful cases. METHODS: The diagnostic features of 11 cases hospitalized for abdominal tuberculosis in the Paediatric Surgery Department of Fattouma Bourguiba Hospital in Monastir for a 6-year period (2001-2006), were evaluated retrospectively. The diagnosis of abdominal tuberculosis was substantiated histopathologically by laparoscopy in all cases. The epidemiological and clinical characteristics along with the laboratory, radiological and histological data were studied. RESULTS: Eleven cases of abdominal tuberculosis with a mean age of 5.6 years were diagnosed. It was peritoneal tuberculosis in all cases and associated with intestinal localization in one case. A conversion to laparotomy was practiced in three patients: appendicular plastron in one case, pseudo-tumor aspect of an intestinal loop in another case and because of their pathological aspect appendicectomy and caecum biopsy in the third. The diagnosis was confirmed histologically by biopsies in nine cases and on excision pieces in the other two cases. All patients had an uneventful course with an antituberculosis treatment. CONCLUSION: Abdominal tuberculosis is still frequent in Tunisia. Because of its non-specific clinical presentation and the limited means of investigation, a laparoscopy with biopsy should be practiced as first line diagnostic tool in case of doubtful abdominal tuberculosis. The earlier the diagnosis is established and an adapted antituberculosis treatment is started, the better the prognosis is.

Epidemiological study of non-polio enterovirus neurological infections in children in the region of Monastir, Tunisia.

The epidemiological, virological, and clinical syndromes of 86 children younger than 13 years suspected of having neurological diseases and admitted to Fattouma Bourguiba Hospital of Monastir from January 2002 to November 2003 were analyzed. The presence of enterovirus was studied in cerebrospinal fluid (CSF) samples by reverse transcription-polymerase chain reaction (RT-PCR) and by isolation on cell culture. Sixty-one (71%) specimens were positive by RT-PCR, whereas 45 (52.3%) were detected by cell culture. Eighty percent (n = 36) of cultured enteroviruses were identified, whereas 20% were untyped. Echoviruses were isolated most frequently, with 32 cases (71.1%) in children. Echovirus 6 was the most commonly identified serotype (22.2%), followed by echovirus 13 (20%). The highest incidence on neurological infection (19.6%) occurred in children less than 6 months of age. The infected children were predominantly male (62.3%). Enteroviruses were detected in all the period of the year with the highest rate in the spring and summer months. Aseptic meningitis was the most commonly diagnosed disease (49%).

Brain MRI and biological diagnosis in five Tunisians MLD patients.

Metachromatic leukodystrophy (MLD) is a recessive autosomal disease which is characterized by an accumulation of sulfatides in the central and peripheral nervous system. It is due to the enzyme deficiency of the sulfatide sulfatase i.e. arylsulfatase A (ASA). we studied 5/200 cases of MLD and clearly distinguished three clinical forms. One of them presented the juvenile form; two presented the late infantile form; and two other presented the adult form. The Magnetic Resonance Imaging (MRI) of these patients showed a diffuse, bilateral and symmetrical demyelination. The biochemical diagnosis of MLD patients evidencing the low activity of ASA and sulfatide accumulation. PATIENTS AND METHODS: We studied 5/200 MLD patients addressed to us for behavioral abnormalities and progressive mental deterioration. All of them were diagnosed at first by brain MRI evidencing a bilateral demyelination, then the measurement of ASA activity using P-nitrocathecol sulfate as substrate, finally the sulfatiduria was performed using thin-layer chromatography using alpha-naphtol reagent. RESULTS: In this study, from 200 patients presenting behavioral abnormalities and a progressive mental deterioration, we reported just 2 patients were diagnosed as late-infantile form of MLD. Only1 case presented as the juvenile form; and 2 patients with the adult-type of MLD. The brain magnetic resonance imaging (MRI) of all patients showed characteristic lesions of MLD with extensive demyelination. Biochemical investigations of these patients detected a low level of ASA activity at 0°C and 37°C; the excess of sulfatide in sulfatiduria. CONCLUSION: MRI is required to orient the diagnosis of MLD patients; the latter must be confirmed by the biochemical investigations which is based on the measurement of ASA activity and the excess of sulfatide showed in the sulfatiduria. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here:http://www.diagnosticpathology.diagnomx.eu/vs/1791578262610232.