FXYD1 is expressed in skeletal muscle and the myocardium, FXYD2 is primarily expressed in kidney epithelial basement membranes, the bile duct and in cholangiocarcinoma cells, FXYD3 is primarily expressed in the liver, pancreas, stomach, colon, prostate, lung, kidney, skeletal muscle and epidermal cells, FXYD4 is primarily expressed in the kidney and distal colon, and FXYD5 is expressed in the brain (7). The gene discussed is FXYD5; the disease is cholangiocarcinoma.