[Clinical characterization of the Stargardt disease and molecular exploration of the c.2041C>T mutation (ABCA4 gene) in Tunisian patients].

Abstract : In order to charaterize the Stargardt disease, the molecular exploration of the c.2041C>T mutation (ABCA4 gene) and genotype phenotype correlation in Tunisian patients, seven unrelated propositi underwent a complete ophthalmological examination. The search for the mutation was performed by a direct sequencing after a specific amplification of exon 14 of the ABCA4 gene. Baseline, the average age of propositi was 20.7 ± 15 years and the sex-ratio was 1.3. The age of the visual impairment perception was 8.1 ± 3.2 years. In all patients, the loss of visual acuity was bilateral and ranged from "counting fingers" to 3.2/10. Fundus and retinal fluorescein angiography examination showed advanced stages of the disease. The allele frequency of the c.2041C>T was 28.5% (4/14). We have reported this mutation in two patients. Their average age at onset was 5 and a half years and the disease progression was rapid with a severe visual loss after 1 and 5 years. All patients had a juvenile macular dystrophy with flavimaculatus flecks. To our knowledge, we reported for the first time the homozygous state of the c.2041C>T mutation. Among homozygous patients, the age at onset was early, the loss of visual acuity was important and the prognosis was severe. Due to the severity of the phenotype and the high rate of inbreeding, genetic counseling for healthy heterozygotes is essential.