Benign monomelic amyotrophy (BMA) is a benign motor neuron disease in which amyotrophic change is confined to either the upper or the lower extremities. Numerous cases of BMA have been reported from Japan and India. However, only a few cases have been reported from other regions, including South Korea. Here we report a rare case of late-onset BMA in Korean male using conventional diagnostic approach with magnetic resonance imaging and electromyography. The patient received ten sessions of manual therapy, which focused on strengthening of the left ankle. At two-month follow up, weakness was still isolated to the patient’s left ankle. There were no signs of disease progression.

Benign monomelic amyotrophy (BMA) is a benign motor neuron disease in which amyotrophic change is confined to either the upper or the lower extremities. Numerous cases of BMA have been reported from Japan and India. However, only a few cases have been reported from other regions, including South Korea. Here we report a rare case of late-onset BMA in Korean male using conventional diagnostic approach with magnetic resonance imaging and electromyography. The patient received ten sessions of manual therapy, which focused on strengthening of the left ankle. At two-month follow up, weakness was still isolated to the patient’s left ankle. There were no signs of disease progression.