| Abstract: | We report here three related patients with a duplication of exons 19–41 of the dystrophin gene, having dissimilar clinical phenotype and dystrophin immunohistochemistry. Two brothers aged six and three years had myalgia, proximal muscular weakness and hypertrophic calves, with 10- to 20-fold increase of serum creatine kinase. Muscle biopsy showed dystrophic changes and reduced, patchy binding of dystrophin. The clinical and laboratory findings were consistent with a diagnosis of Becker muscular dystrophy with early onset. Their 14-year-old cousin had only mild hyperCKemia. His muscle biopsy was normal with only mild reduction of dystrophin immunostaining. At follow-up, he is still without symptoms and signs at age 19. All three patients had the same gene duplication and an increased dystrophin size of 507 kDa. Expression of the dystrophin-associated glycoproteins adhalin,  -dystroglycan, and, β-dystroglycan were normal in the three patients. An intrafamilial variability in patients carrying a partial duplication of the dystrophin gene may be related to a quantitative difference in mRNA. |
