Which clinical history findings are characteristic of spinal muscle atrophy (SMA)?

Updated: Nov 05, 2018
  • Author: Ashish S Ranade, MBBS, MS, MRCS; Chief Editor: Jeffrey A Goldstein, MD  more...
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With type I spinal muscle atrophy (SMA; also known as spinal muscular atrophy), most mothers report abnormal inactivity of the fetus in the latter stages of pregnancy. Babies with type I SMA face many physical challenges, including muscle weakness, trouble breathing, coughing and swallowing. The patient with type I SMA is unable to roll over or sit. Progressive clinical deterioration occurs. Death usually occurs from respiratory failure and its complications in patients by age 2 years.

Patients with type II SMA have normal development for the first 4-6 months of life. They may be able to sit independently, but they are never able to walk. They require a wheelchair for locomotion. They have a longer life span than patients with type I SMA. Some patients with type II SMA live into the fifth decade of life.

In patients with type III SMA, the presenting complaint is difficulty climbing stairs or getting up from the floor (due to hip extensor weakness). Individuals affected by SMA type III are initially able to walk, but as they grow, their mobility is increasingly limited, and they eventually may need to use a wheelchair. The life span is nearly normal. [24]

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