A case of fascioscapulohumeral muscular dystrophy misdiagnosed as Becker's muscular dystrophy for 20 years

A 60-year-old man diagnosed clinically with Becker's muscular dystrophy 20 years ago by another physician presented with gradually progressive proximal muscle weakness since teenage years. Family history revealed a strong paternal familial inheritance pattern of similar distribution of weakness-face, forearm flexion, knee extension and foot dorsiflexion. Work-ups revealed B12 deficiency and allele 1 deletion in fascioscapulohumeral muscular dystrophy (FSHD) DNA testing. FSHD is the third most common muscular dystrophy. Clinical diagnosis is made from the distinctive pattern of weakness, autosomal-dominant inheritance, and confirmed by genetic testing. This case strongly demonstrates the importance of a thorough and careful clinical evaluation even in a case with a long standing diagnosis.