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.