 Importantly, if cysts are found in the medullary collecting ducts they can result in a shrunken kidney, unlike that of polycystic kidney disease.There are two known forms of medullary cystic kidney disease, mucin-1 kidney disease 1 (MKD1) and mucin-2 kidney disease/uromodulin kidney disease (MKD2).A third form of the disease occurs due to mutations in the gene encoding renin (ADTKD-REN), and has formerly been known as familial juvenile hyperuricemic nephropathy type 2.