However, they are at increased risk for complications from respiratory infections. Type II SMA affects infants between seven and 18 months old. Type III patients are able to stand, but weakness is prevalent and tends to eventually sentence its victims to a wheelchair. Type III SMA strikes children after the age of 18 months, but can surface even in adulthood. Type IV is the adult form of the disease in which symptoms tend to begin after age 35.
Symptoms usually begin in the hands, feet and tongue, and spread to other areas of the body.
Facial and tongue muscles are noticeably affected. In addition, these men also often have breast enlargement known as gynecomastia. Like all forms of SMA, the course of the disease is variable, but in general tends to progress slowly. SMA does not affect sensation and intellectual activity in patients. It commonly is observed that patients with SMA are unusually bright and sociable.