Types of SMA
Type 1: Non sitters, never able to sit. Onset before 6 months, most commonly before 3 months. Children have hypotonia and decreased movement of arms and legs, swallowing and feeding difficulties, and impaired breathing. Prognosis is poor with 80% dying by age 1 with the majority of the rest by age 2 (without intervention). Sometimes the most severe cases of type 1 are termed type 0. These babies are born extremely weak and often only survive a few weeks after birth even with intensive respiratory support. 60% of individuals with SMA are type 1.
Type 2: Sitters, unable to walk or stand independently. Onset between 7-18 months. Legs tend to be weaker than arms. May have swallowing difficulties and difficulty with weight gain, weak intercostal muscles (for breathing). May have difficulty coughing and clearing tracheal secretions. 27% of individuals with SMA are type 2.
Type 3: Stand and walk. Onset >18 months and variable. They achieve independent ambulation. Some may lose this ability and childhood while others may maintain until adolescence or adulthood. Swallowing, cough and hypoventilation are less common but may occur.
Type 4: Walk. Onset is usually in the second or third decade of life with mild motor impairment
Types 3 and 4 combined make up ~12% of SMA cases. In general, walkers have relatively preserved pulmonary function until late into their disease course.
LOVE EVERY ONE. PROMOTING AN ALL INCLUSIVE WORLD. SPREADING AWARENESS OF SPINAL MUSCULAR ATROPHY (SMA), FUNDING RESEARCH AND SUPPORTING CHILDREN AND FAMILIES AFFECTED BY CHILDHOOD DISEASES AND DISORDERS.