Neurofilaments as Biomarkers of the Efficacy of Risdiplam Treatment in Early SMA Phenotypes Diagnosed by Newborn Screening.

Risdiplam is an orally administered small molecule that modifies the mRNA splicing of SMN2 for the treatment of spinal muscular atrophy (SMA). Its use is approved in presymptomatic patients diagnosed by neonatal screening with early and severe forms with two copies of SMN2, but we do not have real data on the evolution of oral treatment in this early phenotype of SMA. We present two cases treated at one month of life with a follow-up of 12 months and discuss their different evolutions and the causes of this. Familial adherence to treatment is important, as discontinuation can convert an early form of presymptomatic SMA to symptomatic. Molecular biomarkers such as plasma monitoring of neurofilament light chain (pNf-L) should be considered in the follow-up of early forms of SMA and may support the decision to change treatment in infants with SMA.