Late-onset Hirayama disease presenting with ulnar neuropathy: A case report.

Hirayama disease (HD) was first reported by Hirayama et al. in 1959. The disease is considered as a type of benign focal motor neuron disease that primarily affects upper limbs of young males. In this case report, we present a man aged 40-years with rapidly progressive weakness and atrophy in his left hand. The findings of nerve conduction studies were consistent with left ulnar neuropathy at the elbow. Flexion magnetic resonance imaging (MRI) revealed minimal enlargement of the posterior epidural space and anterior displacement of the spinal cord. After exclusion of relevant diseases the patient was diagnosed as having Hirayama disease with ulnar neuropathy. Mild ulnar entrapment at the elbow may be considered as a clinical feature of HD. Therefore, it is recommended that young male patients with wasting in upper extremities with findings of ulnar entrapment should not be judged to have ulnar neuropathy before HD has been carefully excluded.