SMA Type I Acute (Severe)
Type I SMA is also called Werdnig-Hoffmann Disease. The diagnosis of children with this type is usually made before 6 months of age and in the majority of cases before 3 months, there may be lack of fetal movement in the final months of pregnancy.

Usually a child with Type I, (Werdnig-Hoffmann) is never able to lift his/her head or accomplish normal physical milestones. Swallowing and feeding may be difficult and the child may show some difficulties with their own secretions. There is a general weakness in the intercostals and accessory respiratory muscles (the muscles situated between the ribs). The chest may appear concave (sunken in) due to diaphragmatic (tummy) breathing.

Please note: Although diagnosis may be made before 6 months of age it does not necessarily follow the same course of severity for each patient.


In the acute type of this disease the bulbar muscles are often affected, and this may make feeding and swallowing extremely difficult. Breathing is often labored due to reduced strength of the chest muscles, and most breathing can be seen in the abdominal areas, with the chest appearing sunken in. Because of increased overall weakness or repeat respiratory infections, the prognosis is poor. Death in the majority of children with SMA Type I usually occurs by 2 years of age.