What is Spinal Muscular Atrophy (SMA) ? 1 SMA is a rare inherited disease that weakens muscles over time, making movement difficult. It happens because motor neurons, the nerve cells that control muscles , break down and die . How does it happen? 1 SMA is caused by a fault in a gene called SMN1. This gene normally produces a protein (SMN protein) that keeps motor neurons healthy . When the SMN1 gene is broken, the body doesn’t make enough SMN protein, leading to muscle weakness and wasting. The effect? Without enough SMN protein, muscles get weaker, affecting activities like crawling, walking, swallowing, and in some severe cases - even breathing! Types of SMA: 1 1. Type 1 (Severe) – Symptoms at birth or before 6 months . Weak muscles, breathing/eating difficulties . 2. Type 2 (Intermediate) – Appears at 6– 18 months of age. Babies c an sit but not walk. There is p rogressive deterioration in ...