Diagnostics, clinical and genetic characteristics of Duchenne muscular dystrophy in Kazakhstan

Objective: phenotypic and genotypic description of DMD patients from the southern regions of Kazakhstan. Methods: 103 boys with MD symptoms; retrospective analysis, clinical and genetic studies. Results: 103 boys in the age from 1 to 18 from 6 southern regions of Kazakhstan. The patients’ mean age was 9 years. The dystrophinopathy was confirmed in 64 (62.1%) patients with a referral diagnosis of DMD and was first established in 39 patients (37.9%). DMD phenotype was established in 100 patients (97.1%), IMD - in 3 (2.9%). The average age of the disease onset was 4.3 years, clinical diagnostics - 6.8 years, genetic diagnostics - 8.7 years. The disease ranking by stages: 1 (1%) patient is at the preclinical stage, 77 patients (75.1%) - early and late ambulant stages, 35 patients (34%) - non-ambulant stage. The average age of loss of ambulation was 9.8 years; duration of the walking period - 8.1 years; the duration of the ambulant period 5.4 years were determined in non-ambulant patients. Exon deletions (50.4%) were found in 52 patients, exon duplications (6.7%) in 7 patients. Deletion mutations potentially correctable by 45, 51, 53 exon skipping were found in 17 children (32%). Small and point mutations were found in 45 children (43.6%). Nonsense mutations (n=15) accounted for 14.5% in the overall structure. Conclusion: The average value of the interval between the debut and the final diagnosis was 4.4 years. Analysis showed a short period of the ambulatory stage in non-ambulatory patients (5.4 years).
Keywords: DMD, loss of ambulation, non-ambulant patients, deletions, nonsense mutations