SMN1 and spinal muscular atrophy, type 1: The patient cohort consisted of 9 infants with SMA type 1 (6 males, mean age 25 ± 18.8 months, range 1.7–48 months); all carried a homozygous deletion of exons 7 and 8 in the SMN1 gene on chromosome 5q and had 2 copies of the SMN2 gene (Table 1).