SMN2 and proximal spinal muscular atrophy: Analyzing this in large control cohorts, however, is challenging as short-read sequencing of bisulfite converted DNA samples does not allow to distinguish SMN1 and SMN2 in persons who carry both genes in contrast to SMA patients who only carry copies of SMN2. This may become possible in the future when long-read sequencing allowing haplotype-based analysis becomes more routine and scalable.