Duchenne Muscular Dystrophy (DMD) is an X-linked recessive genetic disorder characterized by rapidly progressive muscle weakness. The disease is caused by deletion, duplication or point mutation of the dystrophin gene, located on the X chromosome (Xp21). Deletion accounts for 60% of the mutations within the 79 exons of the dystrophin gene. Seven exons (43, 44, 45, 46, 49, 50, and 51) were found to be most commonly deleted among the Asian patients. To detect the frequency of deletion of these 7 exons in Malaysian DMD patients, we carried out a molecular genetic analysis in 20 Malaysian DMD patients. The mean age of initial presentation was 60 months (SD 32 months, range 5-120 months). Fourteen patients were found to have deletion of at least one of the seven exons. The remaining six patients did not show any deletion on the tested exons. Deletions of exons 49, 50 and 51 were the most frequent (71.43%) and appear to be the hot spots in our cohort of patients.
Duchenne muscular dystrophy (DMD), the commonest X-linked disorder, is a progressive, eventually fatal disease. With the advent of molecular genetics, the Duchenne gene and its protein product, dystrophin, have been characterised. Molecular diagnosis of DMD, identification of carriers and antenatal diagnosis are now possible. We describe here the use, in a Malaysian boy with DMD, of a recent innovation, multiplex polymerase chain reaction (PCR), to obtain molecular diagnosis by detection of dystrophin gene deletions.
In Duchenne muscular dystrophy (DMD), identification of one nonsense mutation in the DMD gene has been considered an endpoint of genetic diagnosis. Here, we identified two closely spaced nonsense mutations in the DMD gene. In a Malaysian DMD patient two nonsense mutations (p.234S>X and p.249Q>X, respectively) were identified within exon 8. The proband's mother carried both mutations on one allele. Multiple mutations may explain the occasional discrepancies between genotype and phenotype in dystrophinopathy.
We undertook the clinical feature examination and dystrophin analysis using multiplex ligation-dependent probe amplification (MLPA) and direct DNA sequencing of selected exons in a cohort of 35 Malaysian Duchenne/Becker muscular dystrophy (DMD/BMD) patients. We found 27 patients with deletions of one or more exons, 2 patients with one exon duplication, 2 patients with nucleotide deletion, and 4 patients with nonsense mutations (including 1 patient with two nonsense mutations in the same exon). Although most cases showed compliance to the reading frame rule, we found two unrelated DMD patients with an in-frame deletion of the gene. Two novel mutations have been detected in the Dystrophin gene and our results were compatible with other studies where the majority of the mutations (62.8%) are located in the distal hotspot. However, the frequency of the mutations in our patient varied as compared with those found in other populations.