The authors present a case of Hirayama’s disease in a 17- year-old boy who had been complaining, for a year and a half, of pain and unilateral motor deficits in the 4th and 5th fingers of the right hand with progressive functional impairment. On examination, atrophy of the ulnar anterior aspect of the forearm, and right thenar and hypothenar regions was evident, associated with a deficit of muscle strength in t...