rarerelated tag: Reproductive health

Spinal muscular atrophy (SMA) is a genetic disorder characterized by degeneration of lower motor neurons, leading to progressive muscular atrophy, muscle weakness, and muscle paralysis. SMA is usually associated with defect of the survival motor neuron-1 (SMN-1) gene, localized in 5q11.2–q13.3. Classification of SMA is based on the age of onset and maximum motor function milestone achieved: SMA type I (Werdnig–Hoffmann disease) has onset in the first month of life, with a disability to sit unsupported and needing breathing support, with a survival chance of only up to 2-years old; SMA type II has onset between 6 and 18-months old, with the best motor ability to sit alone without support; SMA type III (Kugelberg–Welander disease) has onset between 18 months and 30-years old, with the ability to stand and walk without support; and SMA type IV has adulthood onset and tends to have normal mobility with mild muscle weakness.