abstract:Monomelic amyotrophy (MMA), also known as Hirayama disease, Sobue disease, juvenile non-progressive amyotrophy and juvenile asymmetric segmental spinal muscular atrophy (JASSMA) — is an untreatable, focal motor neuron disease that primarily affects young (15–25 year old) males in India and Japan. MMA is marked by insidious onset of muscular atrophy, which stabilizes at a plateau after two to five years from which it neither improves nor worsens.