Medullary cystic kidney disease

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 1, 2016
StartDiseasesMedullary cystic kidney disease

Medullary cystic kidney disease (MCKD) is an inherited disease. It is incurable, cannot be prevented, and can lead to kidney failure. There are many complications and symptoms which are caused by MCKD and which can be treated or alleviated.

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Definition & Facts

MCKD affects adults only, but there is a similar disease called juvenile nephronophthisis (NPH) that affects children. Both diseases cause cysts in the kidneys and scarring of kidney tissue, which over time will cause the kidneys to lose their ability to function.

MCKD affects only the kidneys, but NPH can also cause problems with the eyes or nervous system. MCKD is uncommon and can be difficult to diagnose. 

MCKD causes the kidneys to be unable to sufficiently concentrate the urine, which in turn causes excessive urine production and the loss of sodium and other elements from the blood. The disease causes small cysts to form in the kidneys. These fluid-filled sacs scar the kidneys and cause the kidneys to fail to perform properly.

Healthy kidneys filter and clean the blood with about 200 quarts of blood passing through the kidneys each day. The clean blood is then sent back to the circulatory system while the waste products and unnecessary fluids become urine. The urine is then passed through the bladder and out of the body.

The damage caused to the kidneys by MCKD results in the kidneys producing urine that is too watery and does not contain the proper amount of waste. The excessive amount of urine that is produced causes the body to lose water, sodium, and other important chemicals.

Symptoms & Complaints

Early symptoms of MCKD may include a craving for salt, excessive urination or urination in the middle of the night, and a feeling of weakness. Untreated, the disease will lead to kidney failure. Other symptoms that may occur in later stages of the disease or complications that may be caused by MCKD include:

Causes

MCKD is an inherited disease with an autosomal dominant inheritance pattern which means that it can be inherited from only one parent. Juvenile nephronophthisis (NPH), on the other hand, requires both parents to carry the gene before it can be passed on to a child. There have been cases where the disease has been found despite no family history of the condition.

Parents who are genetic carriers will pass along one of two types of mutated genes: MUC1 gene or the UMOD gene.

Medullary cystic kidney disease type 1 (MCKD1) is caused by a mutation in the MUC1 gene, which is located on chromosome 1. Medullary cystic kidney disease type 2 (MCKD2) which is also known as uromodulin-associated kidney disease (UAKD) results from a mutation on UMOD gene on chromosome 16, which provides the code for a protein called uromodulin.

In either case, the child of an affected parent will have a 50% chance of inheriting the disease. 

Diagnosis & Tests

There are a number of methods to diagnose MCKD including a physical examination and laboratory tests. Blood tests can be used to test for sodium levels, red blood count, and overall kidney function.

Some individuals may have no early symptoms of MCKD, but may be able to identify the presence of the disease due to elevated creatinine levels in the blood. Additionally, MCKD causes elevated levels of uric acid in the blood which can be identified through a blood test. Elevated creatinine levels are an indicator of reduced kidney functioning.

Genetic testing can confirm the presence of MCKD by analyzing the genes that cause MKD1 and MKD2 to identify mutations. The urine can be tested to determine its concentration.

X-rays, ultrasounds, or computed tomography (CT) scans can be used to measure the size of the kidneys and to look for cysts. A renal ultrasound may show an enlarged or too-small kidney or the presence of cysts in the kidney. A kidney biopsy can also be done where a small piece of the kidney is taken and analyzed in the laboratory. 

Treatment & Therapy

There is no known cure for MCKD and there is no known diet that will slow the progression of MCKD. However, treatment can manage the symptoms of MCKD and may prevent some complications from developing.

Changing the diet to include drinking large amounts of water and a high sodium diet can help to replace fluids and sodium lost through excessive urination. A person with MCKD can easily become dehydrated, and part of the treatment plan may include staying indoors on hot days, avoiding exercise, and avoiding any other activities that could cause dehydration.

Children with MCKD may require growth hormone therapies. MCKD inevitably leads to kidney failure, and at later stages of the disease, dialysis or kidney transplant may become necessary.

Medications may be prescribed to manage symptoms of MCKD such as gout or anemia. Most people who have MCKD will experience end-stage renal disease between the ages of 30 and 50. 

Prevention & Prophylaxis

Because there is no known cure for MCKD, there is no way to prevent the disease. Once MCKD has been diagnosed, it is then critical to manage the disease and any complications that it causes.

Although MCKD is incurable and unpreventable, some of the complications that arise from the disease may be prevented or at least mitigated through preventative treatments such as modified diet and medications.