Clinical Characterization of Patients With 5q Spinal Muscular Atrophy Types 2 and 3 in Brazil: A Cross-Sectional...

Spinal muscular atrophy (SMA), linked to chromosome 5q, is a rare hereditary neurodegenerative disease characterized by progressive motor neuron loss. It is classified into subtypes based on age at onset and the highest motor milestone achieved. This cross-sectional observational study aimed to describe the clinical profile of patients with types 2 and 3 SMA followed within the Brazilian Public Health System (SUS). Clinical data from patients with types 2 and 3 SMA followed at nine national reference centers (2020-2021) were analyzed. A total of 155 patients were included: 76 with type 2 and 79 with type 3 SMA. Disease duration was longer in type 3 patients. Time from symptom onset to genetic confirmation was also longer in this group. Functional impairment was observed in both subtypes. Type 2 patients had lower HFMSE scores overall, though higher scores were seen among those on disease-modifying therapies. In type 3, earlier symptom onset and longer disease duration were associated with worse motor outcomes. HFMSE scores varied with treatment use and disease duration. Findings reveal the clinical heterogeneity of SMA and emphasize the impact of diagnostic delays and disease duration on function. Early diagnosis and ongoing multidisciplinary care are crucial.