What is the prognosis of spinal muscle atrophy (SMA)?

Updated: May 04, 2020
  • Author: Ashish S Ranade, MBBS, MS, MRCS; Chief Editor: Jeffrey A Goldstein, MD  more...
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The age of onset and the achievement of functional abilities are better predictors of prognosis than the number of copies of SMN2. Genetic modifiers (eg, PLS3) may also influence disease severity and prognosis. [16]

As a general rule, the younger the patient at disease onset, the worse the prognosis. The overall median age at death exceeds 10 years. Intelligence is unaffected by SMA. Patients with type I SMA usually die by age 2 years. Patients with type II SMA have a greater expected lifespan than patients with type I SMA. Some patients with type II SMA live into the fifth decade of life. Patients with type III SMA have nearly normal life expectancy.

Death occurs as a result of respiratory compromise. The lifespan of affected individuals has significantly increased with the use of intermittent positive-pressure ventilation (PPV), with or without a tracheostomy.

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