Here is a cut section of a kidney with autosomal recessive polycystic kidney disease (ARPKD). Note that the cysts are fairly small but uniformly distributed throughout the parenchyma so that the disease is usually symmetrical in appearance, with both kidneys markedly enlarged. The recurrence risk for this disease is, of course, 25% because of the autosomal recessive inheritance pattern. Affected babies usually do not survive long.

Question: What gene mutation is most likely present with ARPKD?

AnswerARPKD is linked to an abnormal fibrocystin protein encoded by the PKHD1 gene. Fibrocystin is expressed on cilia of both renal tubular and bile duct epithelial cells, explaining the renal cysts and the congenital hepatic fibrosis.