Spinal Muscular Atrophy Type I

Spinal Muscular Atrophy Type I generally appears or is diagnosed in infants ages 0-6 months - the majority of diagnoses being made within the first three months of life. Also known as Infantile SMA or Werdnig-Hoffman disease, it is the most severe form of Spinal Muscular Atrophy. It generally has a quick and unexpected onset after birth, and babies diagnosed with SMA Type I usually do not live past one year of age.

A child with SMA Type I is usually never able to lift his/her head and have trouble accomplishing the normal motor skills that are milestones in early infancy. Some of the most noted symptoms include not only poor head control, but also the inability to sit up unsupported, leg movements that are not as vigorous as they should be, and not bearing weight on the legs. Swallowing and feeding are usually affected as well, and they almost always become affected at some point. This can be linked in some ways to another symptom - atrophy of the tongue. This particular atrophy is most commonly marked by rippling movements or fine tremors of the tongue, which are referred to as fasiculations. Finally, some mothers may note decreased movement of the fetus while still in the womb.

An SMA patient's strongest breathing muscle is the diaphragm - most likely due to a weakness of the intercostal muscles, which are located between the ribs and help to expand the chest, that usually results in a smaller torso. The patient's chest may appear to be concave, and it looks like they are breathing with their stomach. Due to this type of breathing, the lungs may not fully develop, which can lead to a weak cough and difficulty taking the deep breaths necessary to maintain oxygen levels while sleeping. This means that the most common cause of death in patients with SMA Type I is respiratory failure due to these complications or because of infection.