ICD-10 Specific code G12.0: Infantile spinal muscular atrophy, type I [Werdnig-Hoffman]

Nusinersen is an antisense oligonucleotide (ASO) which increases the proportion of exon 7 inclusion in survival motor neuron 2 (SMN2) messenger ribonucleic acid (mRNA) transcripts by binding to an intronic splice silencing site (ISS-N1) found in intron 7 of the SMN2 pre-messenger ribonucleic acid (pre-mRNA) and hence when SMN2 mRNA is produced, it can be translated into the functional full length SMN protein. SMA is a progressive neuromuscular disease resulting from mutations in chromosome 5q in the SMN1 gene. Gene SMN2, located near SMN1, is responsible for a small amount of SMN protein production.

Onasemnogene abeparvovec is a gene therapy designed to introduce a functional copy of the survival motor neuron gene (SMN1) in the transduced cells to address the monogenic root cause of the disease. By providing an alternative source of SMN protein expression in motor neurons, it is expected to promote the survival and function of transduced motor neurons.

Risdiplam is a survival of motor neuron 2 (SMN2) pre-mRNA splicing modifier designed to treat SMA caused by mutations of the SMN1 gene in chromosome 5q that lead to SMN protein deficiency. Functional SMN protein deficiency is directly linked to the SMA pathophysiology which includes progressive loss of motor neurons and muscle weakness. Risdiplam treats SMA by increasing and sustaining functional SMN protein levels.