I, or Werdnig-Hoffman Disease, is the most severe form of SMA.
Children with Type I tend to be weak and lack motor development,
rendering movement difficult. Children afflicted with Type I cannot
sit unaided and have trouble breathing, sucking and swallowing. Type
I SMA strikes infants between birth and six months.
II is slightly less severe. Type II patients may be able to sit
unaided or even stand with support and usually do not suffer from
feeding and swallowing difficulties. However, they are at increased
risk for complications from respiratory infections. Type II SMA
affects infants between seven and 18 months old.
III, also known as Kugelberg-Welander disease, is the least deadly
form of childhood-onset SMA. 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.
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.
Onset X-Linked SMA, also known as Kennedy's Syndrome or Bulbo-Spinal
Muscular Atrophy, occurs only in men. 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.
does not affect sensation and intellectual activity in
patients. It commonly is observed that patients with SMA are
unusually bright and sociable.