In agreement with an expected more active disease in pediatric patients compared to adult, mostly milder and chronic, SMA forms (Yeo and Darras, 2020), we found that at baseline (i.e., before nusinersen treatment) the levels of TNF-α, a pivotal cytokine released from Th1 and Th17 cells, was increased only in pediatric patients’ sera. The gene discussed is TNF; the disease is proximal spinal muscular atrophy.