MYOTONIC DYSTROPHY: CLINICAL AND MOLECULAR SPECTRUM IN KWA ZULU NATAL, SOUTH AFRICA

Background and Purpose Myotonic dystrophy is the commonest form of adult muscular dystrophy. Myotonic dystrophy type 1 and 2 are autosomal dominant inherited multisystemic disorders. Type 1 presents with predominantly distal weakness. Type 2 has predominantly proximal weakness. Type 1 is caused by the expansion of an unstable CTG trinucleotide repeat. Type 2 is caused by a tetranucleotide, CCTG expansion. All mutations can be detected using a combination of Southern Blot and Polymerase Chain reaction (PCR) techniques. This study aims to characterize the clinical spectrum and molecular features of myotonic dystrophy patients in Kwa Zulu Natal, a province in South Africa. Method Patients included in this study were obtained from the database of patients diagnosed between 1989 to 2004. Patients were subjected to clinical, radiological and neurophysiological assessment and molecular testing. Results Thirty seven patients were identified. Twenty patients consented and were included in the study. Eighty five percent of patients were of Indian decent and the remaining fifteen percent were White. No African patients were identified. Myotonia was clinically present in all patients. Ninety five percent of patients presented with predominantly distal weakness. Southern blotting demonstrated expanded CTG repeats in all 20 samples. The PCR analysis was unable to demonstrate expanded alleles. Conclusion This study demonstrated that Type 1 remains the commonest clinical and molecular presentation. It supported previous findings in which no South African of African decent was found to be affected by the disease. Southern Blotting remains the gold standard in obtaining a molecular diagnosis, however clinical diagnosis is sufficient.