PXK and systemic sclerosis: This variant is present in 10.4% of the Turkish, 15.4% of the German, and 2.5% of the Mexican population, with a mean allele frequency of 0.052, 0.077, and 0.017, respectively (13) and is associated with an increased risk of anticentromeric-positive systemic sclerosis, rheumatoid arthritis, idiopathic inflammatory myopathies, and SLE (where it is often identified as a SNP in a neighboring gene, PXK) (15, 18, 49–51).