Abstract
IntroductionDuchenne Muscular Dystrophy (DMD), an X-linked recessive genetic disorder is maternally inherited in approximately two-thirds of affected boys. Female relatives have carrier risk. This study proposes that proactive genetic screening and counselling for patients’ relatives, contributes to reductions in preventable cases and ultimately disease incidence.MethodsA retrospective study of cases born in NSW from 1991–2013 was completed, using an electronic database of live male and prenatally diagnosed patients with DMD, referred to our tertiary service. Proband genotype/phenotype, pedigree, carrier-risk and extent of cascade screening were reviewed. Variance analysis (two-way ANOVA) was used to analyse changing trends in preventable cases.Results77 cases were identified. Mean age at presentation fell by 14-months over time. Probands were defined as ‘theoretically preventable’ when disease was identified in previous generations, or in males aged over 6 years, within the same generation. Fifteen (19%) cases were preventable, with a statistically significant decline in such cases over time.Cascade screening and prenatal testing of subsequent pregnancies was offered to all carrier mothers and female relatives in the mother’s generation. Fifteen women underwent prenatal testing. Three affected male foetuses were identified, with one live affected male being born, after parents proceeded with the pregnancy.ConclusionRigorous and expansive approaches to cascade-screening/counselling may account for decreases in preventable cases. Age of diagnosis has fallen, providing potential for more timely intervention, aided by newer diagnostic techniques that allow more accurate proband genotyping. Prenatal testing identified small numbers of affected males, facilitating parental decision-making in these select cases.
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