The index SNP on chromosome 2q21 maps into MCM6, upstream of the lactase gene LCT. The index variant is in perfect linkage disequilibrium (LD) with rs4988235, a variant associated with lactose intolerance in ClinVar and OMIM (#223100), which functions as an enhancer of the LCT gene promoter in intestinal cell culture13. The gene discussed is LCT; the disease is lactose intolerance.