SMA is divided into subtypes based on the age of onset, and maximum function achieved. SMA types 0, 1, 2, 3 and 4 are inherited as autosomal recessive genetic disorders, and are associated with mutations in the SMN1 gene which is located on chromosome 5.1
Spinal Muscular Atrophy Type 0
SMA type 0, or Prenatal SMA,2 is the most severe form of SMA and is characterized by decreased fetal movements in utero (between 30 and 36 weeks of pregnancy)3, and by joint abnormalities, difficulty swallowing, and respiratory failure at birth.4
Type 0 results from a partial or complete loss of the SMN1 gene, and about 95% of the babies affected will show a deletion of both copies of a specific portion (exon 7 and 8) of the gene.
Infants with SMA type 0 often succumb to the disease before the age of 6 months (usually, between 2 and 6 months of age), and they do not develop any motor skills expected of infants their age.5 Type 0 patients’ in utero signs of diminished fetal movements and issues with asphyxia and severe weakness directly at birth6 distinguishes the phenotype from type 1 SMA, which usually presents at birth or within the first few months of life.
Follow the latest developments for all experimental Spinal Muscular Atrophy treatments on the SMA Therapy Tracker.
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