[Spinal muscular atrophy: Clinical and genetic aspects, and therapeutic alternatives]

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by a mutation in the SMN1 gene, located on chromosome 5q13. It is characterized primarily by neuronal degeneration due to a deficiency in producing full-length survival motor neuron protein (FL-SMN), which results in progressive muscle weakness with complications such as scoliosis, paralysis, and even death. This article reviews the clinical and genetic aspects of the disease, its diagnosis and classification, as well as therapeutic alternatives. In this context, it highlights the role of the molecular determination of the causal genetic variant and the copy number of the homologous SMN2 gene as the primary modifiers of the course of the disease, both for diagnosis and classification, as well as for therapeutic decision making. Recently, therapies focused on modifying the natural history of SMA by increasing FL-SMN protein production have been developed. Currently, 3 treatments are available: Spinraza (nusinersen), Zolgensma (onasemnogene abeparvovec), and Evrysdi (risdiplam). Studies performed with these drugs to confirm their safety and efficacy show favorable results; however, early diagnosis is decisive for the success of any of these therapeutic alternatives.