SMN2 and proximal spinal muscular atrophy: Here, we investigate ancestral chromosome 5 haplotypes in relation to SMA phenotype among 42 Mennonite and 14 Amish individuals harboring 2 (n = 44), 3 (n = 9), or 4 (n = 3) copies of SMN2. This is the first comprehensive clinical description of SMA within Plain communities and provides a unique lens through which to view the natural history of disease undistorted by technological interventions, genetic variability, and heterogenous approaches to care.