Which physical findings are characteristic of type I 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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Newborns with type I SMA are floppy and inactive. They move the extremities little, if at all. The hips are flexed, abducted, and externally rotated. The knees are flexed. Because the distal musculature is usually spared, the fingers and toes move. Infants cannot sit independently or control or lift the head. They have a weak cry and cough. They have difficulty with swallowing and feeding. They have a bell-shaped trunk with chest-wall collapse and abdominal protrusion with paradoxical breathing. Areflexia is universal.

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