Spinal Muscular Atrophy in the Age of Gene Therapy

Spinal muscular atrophy (SMA) is a rare autosomal recessive neurodegenerative disease affecting 1 in 10,000 to 11,000 births,^1,2  approximately 400 infants in the United States each year.³  Spinal muscular atrophy is the most common fatal genetic disease of infancy.^1,4  Unlike with other degenerative motor neuron diseases, the greatest loss of motor strength and function occurs at the onset of SMA; the disease then progresses slowly, until, in many cases, early death.⁵  Clinical presentation includes a wide range of phenotypes that are classified into groups based on age at disease onset, maximal motor function achieved, clinical course, and survival^6,7  (see Table).

Spinal muscular atrophy type 1, also known as acute infantile SMA or Werdnig-Hoffman disease, is the most common and severe form seen in the acute care setting.¹⁰  Reports of impaired fetal movements are observed in 30% of...