Takeaway
SMN2 copy number appears to be the most important predictor of the clinical phenotype in individuals with spinal muscular atrophy.
Why this matters
Greater understanding of genetic variants that underlie clinical heterogeneity in spinal muscular atrophy is urgently required to improve neonatal screening programs and therapeutic strategies. The observation that gene copies of SMN2 are structurally different both between and within individuals could have important consequences for current counselling and treatment practices.