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

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

In these conditions, the kidneys don't concentrate the urine enough, leading to excessive urine production and loss of sodium. Salt supplementation may be required. Additional kidney problems follow. Most MCKD patients reach end-stage kidney disease between the ages of 30 and 50. NPH patients are about 4 years of age when it begins.

NPH may be associated with non-kidney features (like abnormalities in the eyes), while MCKD is limited to the kidneys only.

Early in the course of the disease, the symptoms include:

• Need to urinate at night (nocturia)
• Excessive urination (polyuria)
• Weakness
• Low blood pressure
• Need for excessive salt intake

Late in the disease, the symptoms of kidney failure may develop:

• Pale skin
• Weakness
• Unintentional weight loss
• Nausea, vomiting
• General ill feeling
• Fatigue
• Headache
• Frequent hiccups
• Generalized itching
• Easy bruising or bleeding (such as vomiting blood or blood in the stool)
• Decreased alertness, drowsiness, lethargy, confusion, delirium, coma
• Muscle twitching or muscle cramps
• Seizures
• Increased skin pigmentation (skin may appear yellow or brown)
• Reduced sensation in the hands, feet, or other areas

Early in the course, the physician may identify:

• The patient is passing large amounts of diluted urine, with salt wasting.
• The urine specific gravity is low and fixed.
• Blood pressure may be low and require salt supplements.

The diagnosis can be established with:

• Abdominal ultrasound or abdominal CT scan - these may show small kidneys or multiple cysts on the kidneys
• Renal biopsy -- this may show tubulo-interstitial nephropathy and medullary cysts.

As the disease progresses, kidney failure follows:

• Increasing creatinine levels
• Increasing BUN (blood urea nitrogen)
• Decreasing creatinine clearance
• Elevated blood pressure
• Anemia (shown on complete blood count)
• Small, shrunken kidneys (shown on ultrasound)

There is no cure for this disease. At first, treatment focuses on controlling symptoms, minimizing complications, and slowing the progression of the disease. Because of the loss of water and salt, the patient will need a liberal intake of both to avoid dehydration.

As the disease progresses, kidney failure develops and appropriate changes will be made:

• If high blood pressure develops, anti-hypertensive medications may be needed.
• Anemia may require erythopoeitin treatment to build red blood cells.
• Diet will be modified to limit phosphorous- and potassium-containing foods.

Once end-stage kidney disease approaches, dialysis may be started. If a suitable donor becomes available, a kidney transplant may be performed.

• Hyponatremia, a disorder of fluid and electrolyte imbalance
• End-stage kidney disease
• Pericarditis, cardiac tamponade
• Platelet dysfunction
• Gastrointestinal bleeding, ulcers
• Hemorrhage
• Anemia
• Peripheral neuropathy
• Weakening of the bones, fractures, joint disorders
• Permanent skin pigmentation changes
• Itching
• Changes in glucose metabolism
• Changes in electrolyte levels, electrolyte abnormalities including hyperkalemia
• Miscarriage, menstrual irregularities, infertility
• Congestive heart failure
• Hypertension