Monomelic amyotrophy or Hirayama disease, is a rare motor neuron disorder characterized by progressive weakness and atrophy in the distal upper extremities, typically beginning during adolescence. The condition involves asymmetric muscle atrophy in the hand and forearm, sparing the brachioradialis muscle, and is attributed to increased laxity in the dura mater, which causes the spinal cord to shift forward during neck flexion. This movement results in repetitive microtrauma to the lower cervical spinal cord, leading to muscle denervation. Diagnosis relies on postcontrast neutral and flexion magnetic resonance imaging, which reveals characteristic crescent-shaped enhancement and epidural flow voids. We report a case of HD in a male patient in his 20s with gradual bilateral upper limb weakness and wasting, confirmed by imaging and nerve conduction studies.