[A case of female dystrophinopathy with presumed childhood onset, presenting with asymmetric muscle weakness and delayed diagnosis in old age].

Duchenne and Becker muscular dystrophies are X-linked disorders that predominantly affect men; however, women can also develop symptomatic dystrophinopathy. We report a case of female dystrophinopathy characterized by childhood-onset motor difficulties, which evolved into slowly progressive, asymmetric muscle weakness in adulthood. The patient was a 79-year-old woman who had difficulty running since childhood but maintained independence in performing activities of daily living for many years. She began to experience gait difficulty at ~62 years of age, with gradually progressive muscle weakness that showed marked asymmetry. During initial evaluation at 68 years of age, skeletal muscle imaging revealed asymmetric muscle involvement suggestive of dystrophinopathy. A muscle biopsy demonstrated dystrophic changes; however, genetic testing was not performed at that time due to a lack of health insurance coverage. Thus, a definitive diagnosis could not be established. Upon further disease progression, the patient was re-evaluated at 79 years of age. On re-assessment, immunohistochemistry of the muscle biopsy revealed a mosaic pattern of dystrophin expression. Subsequent genetic analysis using multiplex ligation-dependent probe amplification identified a heterozygous deletion of exons 45-52 in the dystrophin gene that lead to an ultimate diagnosis of female dystrophinopathy. Clinical and radiological findings of asymmetric muscle distribution was considered characteristic of symptomatic female carriers. The clinical manifestations of dystrophinopathy in women are highly variable, and the absence of an apparent family history often contributes to a delayed diagnosis. The present case highlights the diagnostic challenges associated with female dystrophinopathy and underscores the importance of consideration of this condition in women presenting with progressive muscle weakness, particularly when marked asymmetry is evident. Early recognition and appropriate genetic testing are essential for establishing an accurate diagnosis, clinical management, and long-term follow-up, including surveillance for potential cardiac and central nervous system involvement.