Unmasking distal upper limb atrophy – Hirayama disease

Abstract

Hirayama disease is an uncommon, non-progressive juvenile amyotrophy that predominantly affects young Asian males. It typically presents with insidious onset distal upper limb weakness and muscle wasting without sensory involvement. Early recognition is important, as timely diagnosis can prevent disease progression. We report the case of a 28-year-old male with gradually progressive weakness and wasting of the distal upper limb muscles, exacerbated by cold exposure, and without sensory deficits. Flexion magnetic resonance imaging revealed a long-segment posterior dural detachment extending from C5 to D3 with associated cervical cord compression. Electrophysiological studies demonstrated denervation changes with preserved sensory conduction. The patient was managed conservatively with a cervical collar, following which his clinical condition stabilized. This case highlights the clinical and radiological variability of Hirayama disease. It reinforces the importance of flexion MRI in establishing an early diagnosis and supports conservative, non-surgical management in clinically stable cases.