Clinical features of Hirayama disease in mainland China.

The aim of this study was to investigate patients with Hirayama disease in mainland China. A total of 192 patients (167 males, 25 females) collected from mainland China were included. Their clinical features, electrophysiology, imaging, muscle biopsy and laboratory tests, treatments, and prognosis were analysed. We compared the results with data from other countries or regions. The mean age at onset was 16.8 years. Onset was insidious, with symptoms of muscle weakness and atrophy in the distal muscles of the upper limb. Tremor on finger extension was noted in 77.6% of patients and cold paresis in 81.3%. The clinical course plateaued within five years in 89.1% of patients. Time from disease onset to definitive diagnosis of our series is longer than that from other countries or regions. There is no geographically based difference in the clinical presentation of Hirayama disease. Thus, our study supports the notion that Hirayama disease is a benign self-limited disorder with juvenile preponderance and asymmetric muscular atrophy of the distal portion of the upper limb. Hirayama disease is under-recognized in mainland China.