We chose to investigate the post‐synaptic protein neurogranin as its increase was linked to cognitive decline in patients with Alzheimer's disease possibly reflecting synaptic dysfunction and degeneration35, 36, 37 Cognitive function in children and adolescents with all SMA types has been reported within the normal range,38 but cognitive data of adult SMA patients or long‐term surviving SMA type 1 patients are missing or heterogeneous. Here, NRGN is linked to early-onset autosomal dominant Alzheimer disease.