Becker Phenotype Muscular Dystrophy in a Man with Klinefelter Syndrome: A Rare Association

To present a rare clinical case of a man affected simultaneously by Becker phenotype Muscular Dystrophy (<em>MD</em>) and Klinefelter syndrome and the way how he was diagnosed. A 35-year-old man was evaluated in the context of hospitalization for respiratory failure. Since childhood, he had a clinical and muscle biopsy diagnosis of muscular dystrophy, possibly type Becker. His physical examination showed severe weakness of the pelvic and shoulder girdle, with a waddling gait, grade II scoliosis associated with tall height, obesity, and hypogonadism. Banding cytogenetics detected a sexual trisomy, 47, XXY in ~64% of peripheral blood cells. A heterozygote missense mutation in the dystrophin gene (<em>DMD)</em> was found in parallel using next-generation sequencing. Biparental origin, both X chromosomes suggest nondisjunction in paternal meiosis I, followed by a postzygotic trisomic rescue in a subset of fetal cells during embryonic development. Maternal inheritance of the <em>DMD</em> gene mutation was excluded, suggesting a <em>de novo</em> origin. This is the eighth case where Klinefelter syndrome and Becker phenotype Muscular Dystrophy are parallel. As the patient presents with relatively mild MD symptoms for his age, a skewed X-inactivation pattern in the 47, XXY cell line may be suggested.