PRKCA and myeloid sarcoma: To monitor for potential difference in background allele frequencies between two populations, we selected the ten most centromeric SNPs (rs724560–rs4630583, see Table S2), which did not show evidence for association to MS and were not in linkage disequilibrium (LD) with the SNPs of the PRKCA gene, and performed comparisons between Finns and Canadians using Genepop (Genepop on the Web [http://wbiomed.curtin.edu.au/genepop], option 3: population differentiation).