Climatic droplet keratopathy (CDK) is rare acquired, often bilateral, degenerative corneal disease that frequently occurs in certain indigenous populations chronically exposed to harsh environmental conditions. We are investigating the genetic basis of the disease in Mapuche Indians from northwest Argentina. To date, we have examined variation in the mtDNAs, Y-chromosomes, and HLA-DRB1 genes in the Mapuche to assess genetic background effects on the disease. Rachel Gittelman also sequenced the ALDH3A1 gene to determine if any variants were associated with CDK. ALDH3A1 encodes a protein that protects the mammalian cornea against harmful UV radiation, making it a good candidate gene in the etiology of the disease.