HBB and Schnyder corneal dystrophy: rs33930165 is a nonsynonymous HBB SNP in the same codon as rs334; the risk allele, T, changes the amino acid to a lysine resulting in hemoglobin C. Compound heterozygotes of the risk alleles of rs33930165 (T allele) and rs334 (A allele) can cause SCD16; rs33930165 TT homozygous individuals have mild anemia, but not SCD.49