Early Diagnosed Hirayama Disease with Unusual Symptoms Improved by Steroid Pulse Therapy

Background: Hirayama disease (HD), or monomelic amyotrophy, is a benign neurologic disorder mostly affecting young Asian men. It usually presents with unilateral or bilateral muscular atrophy and weakening of the upper limbs. We treated a patient with HD with bilateral hand paresthesia and weakness in 1 hand and both legs. To our knowledge, this is the first HD case including lower extremity weakness and sensory abnormalities. We improved the patient's symptoms by administering steroids in parallel with conservative treatment. Case Description: A 22-year-old man visited our clinic with bilateral hand paresthesia and weakness in the right hand and both legs. He had been affected 40 days. Results of blood and cerebrospinal fluid tests were normal. Evoked potential study and brain magnetic resonance imaging (MRI) were normal. In cervical MRI, however, a lesion with high signal intensity of the C6 level on T2-weighted images was confirmed, and gray and white matter were extensively invaded. We performed empirical steroid pulse therapy before the results of blood tests to differentiate spinal demyelinating disease. MRI with neck flexion showed HD-related findings, and autoantibody tests showed no specific findings. After steroid pulse therapy, his neurologic symptoms improved within 7 days, leaving only paresthesia of toes of both feet when discharged. Conclusions: HD occurs at a young age and therefore can damage quality of life. Although the patient had unusual symptoms, the condition was diagnosed quickly, and his symptoms improved with steroid therapy. If HD is suspected, additional tests such as MRI with neck flexion should be performed and early steroid treatment might be considered.