Medullary cystic kidney disease (MCKD) is a hereditary disorder in which cysts in the center of each kidney cause the kidneys to gradually lose their ability to work.

Medullary cystic kidney disease (MCKD) is very similar to the childhood disease familial juvenile nephronophthisis (NPH). Both lead to scarring of the kidney and formation of fluid-filled cavities (cysts) in the deeper parts of the kidney.

In these conditions, the kidneys don't concentrate the urine enough, leading to excessive urine production and loss of sodium and other chemical changes in the blood and urine.

MCKD occurs in older patients and is inherited in an autosomal dominant pattern. NPH occurs in young children and is usually due to autosomal recessive inheritance.

NPH may be associated with non-kidney features (like eye problems), while MCKD is limited to the kidneys.