Hirayama is a rare nonfamiliar monomelic amyotrophy also known as benign juvenile brachial spinal muscular atrophy, juvenile asymmetric segmental spinal muscular atrophy, juvenile muscular atrophy of the distal upper extremity, monomelic amyotrophy, and oblique amyotrophy. Classically, it presents with muscle atrophy and weakness of bilateral or unilateral forearms and hands in the absence of sensory […]