Homozygous female Becker muscular dystrophy

We report, for the first time, on a female Becker muscular dystrophy (BMD) patient with homozygous dystrophin deletion. The 14-year-old patient, product of consanguineous parents, presented with a 7-year history of exercise intolerance and recurrent myoglobinuria. Although CK was elevated to 1,800 U/L, no muscle weakness, atrophy, or hypertrophy was seen on examination. Muscle pathology demonstrated a minimal dystrophic change and faint dystrophin staining pattern. Semi-quantitative PCR of dystrophin revealed a homozygous dystrophin deletion of exons 45-55, which is predicted to remove 593 amino acids without frame shifting. Western blot analysis of skeletal muscle for dystrophin showed a 306 kDa band; thus, we made a diagnosis of female BMD. We confirmed identical deletion in both father and mother, in hemizygous and heterozygous modes, respectively. Neither female Duchenne muscular dystrophy (DMD) nor BMD due to homozygous dystrophin mutation has ever been identified although female DMD has been found in patients with Turner syndrome or unilateral parental disomy for X chromosome. Our results indicate that dystrophinopathy can also be caused in females by homozygosity, albeit rare.