what is sma type 2

Spinal Muscular Atrophy (SMA) Type 2, also known as Dubowitz disease, is a genetic neuromuscular disorder characterized by muscle weakness that typically appears in children between 6 and 18 months of age. Children with SMA Type 2 can usually sit independently but are unable to walk. The disease causes progressive proximal muscle weakness (mainly in the legs), hypotonia (low muscle tone), and may be accompanied by symptoms like finger tremors, scoliosis (curvature of the spine), joint contractures, and respiratory muscle weakness that can lead to serious breathing problems. Most individuals with SMA Type 2 have mutations in the SMN1 gene and typically have three copies of the SMN2 gene, which affects the severity of the condition. The condition is inherited in an autosomal recessive manner, meaning a child must inherit defective genes from both parents to develop the disease. The life expectancy for people with SMA Type 2 varies, with many surviving into early adulthood, and treatments including gene therapy and supportive therapies like physical and respiratory therapy can improve quality of life and outcomes. Cognition remains normal in affected individuals. SMA Type 2 is the intermediate form of SMA and is more severe than Type 3 but less severe than Type 1, which appears earlier and is more debilitating. It is considered a rare disease but is the second most common severe hereditary disease in infancy and childhood after cystic fibrosis.