Hirayama disease with proximal upper limb involvement in an adolescent female

INTRODUCTION AND IMPORTANCE: Hirayama disease is a rare benign motor neuron disorder that involves a single upper limb. It affects the lower cervical myotomes and presents clinically by muscle wasting and weakness. CASE PRESENTATION: We report the case of a 17-year-old female who presented with a four weeks history of progressive weakness of the left upper limb. The blood investigations and image reported unremarkable findings. Patient improved on physiotherapy. CLINICAL DISCUSSION: Hirayama disease is rarely encountered in clinical settings and should be suspected in female patients presenting with unilateral or asymmetrical bilateral lower motor weakness of hands and forearms. CONCLUSION: We present a rare condition in a 17-year-old female with a left upper extremity monomelic amyotrophy, a Hirayama disease.