RESUMEN
Autosomal recessive cerebellar ataxias (ARCA) constitute a highly heterogeneous group of progressive neurodegenerative disorders that typically occur prior to adulthood. Despite some clinical resemblance between these disorders, different genes are involved. We report in this study four Tunisian patients belonging to the same large consanguineous family, sharing autosomal recessive cerebellar ataxia phenotypes but with clinical, biological, electrophysiological, and radiological differences leading to the diagnosis of two distinct ARCA caused by two distinct gene defects. Two of our patients presented ataxia with the vitamin E deficiency (AVED) phenotype, and the other two presented ataxia with oculo-motor apraxia 2 (AOA2). Genetic testing confirmed the clinical diagnosis by the detection of a frameshift c.744delA pathogenic variant in the TTPA gene, which is the most frequent in Tunisia, and a new variant c.1075dupT in the SETX gene. In Tunisia, data suggest that genetic disorders are common. The combined effects of the founder effect and inbreeding, added to genetic drift, may increase the frequency of detrimental rare disorders. The genetic heterogeneity observed in this family highlights the difficulty of genetic counseling in an inbred population. The examination and genetic testing of all affected patients, not just the index patient, is essential to not miss a treatable ataxia such as AVED, as in the case of this family.
Asunto(s)
Ataxia Cerebelosa , Activador de Tejido Plasminógeno , Deficiencia de Vitamina E , Humanos , Ataxia/genética , Ataxia Cerebelosa/genética , Ataxia Cerebelosa/epidemiología , Consanguinidad , ADN Helicasas/genética , Heterogeneidad Genética , Enzimas Multifuncionales/genética , Mutación , ARN Helicasas/genética , Activador de Tejido Plasminógeno/genéticaRESUMEN
CLCN2-related leukoencephalopathy (CC2L OMIM#: 615651) is a recently identified rare disorder. It is caused by autosomal recessive mutations in the CLCN2 gene and leads to the dysfunction of its encoded CLC-2 chloride channel protein with characteristic brain MRI features of leukoencephalopathy. We report the first Tunisian patient with clinical features of ClCN-2-related leukoencephalopathy. A 54-year-old female with a family history of leukemia, male infertility, motor disability, and headaches who initially presented with a tension-type headache and normal physical examination. At the follow-up, she developed mild gait ataxia and psycho-cognitive disturbances. A previously reported homozygous NM_004366.6(CLCN2):c.1709G > A (p.Trp570Ter) stop gained mutation was identified. This report expands the knowledge related to CC2L and highlights the clinical features in affected individuals of African descent.