Mucin-1 Kidney Disease (MKD) was previously known as:
- Medullary cystic kidney disease
- Medullary cystic kidney disease Type 1
MKD is a rare inherited kidney disease that causes progressive kidney failure leading to the need for a kidney transplant or dialysis in most patients. There are about 200 families worldwide that have been identified with this disease. MKD is caused by a mutation in one copy of the MUC1 gene. This mutation causes MUC1 to be made abnormally. The abnormal MUC1 accumulates in the tubule cells within the kidneys, leading to slow loss of kidney function.
In MKD, patients slowly lose kidney function over time. The kidneys are bean-shaped organs, about the size of a fist. They are located in the back next to the spinal column. Healthy kidneys filter and clean about 200 quarts (liters) of blood every day, removing excess water, minerals, and wastes.
The kidneys also produce hormones that make red blood cells and control blood pressure. They make active Vitamin D, which the body uses to keep your bones strong.
Kidney failure is usually determined by a blood test, called the blood creatinine level. Creatinine is a waste product that your muscles produce as they work. Healthy kidneys will filter creatinine into the urine, while damaged ones will not. Because damaged kidneys cannot filter creatinine well, it stays in the bloodstream and the blood creatinine level rises.
Blood creatinine is part of a group of tests that may be done as part of a routine physical or before surgery. MKD may be first identified when an elevated creatinine is found on a routine blood test done for other reasons.
In MKD, blood creatinine levels rise slowly over years as the kidneys become more damaged. Once the levels rise to a certain level, usually above about 6 mg/dL (milligrams per deciliter) or about 530 mmol/L (millimoles per liter), the patient must begin dialysis or have a kidney transplant.
How Will MKD Make Me Feel?
Many people do not even know they have a kidney disease until their blood creatinine levels rise very high and they lose a lot of kidney function. They usually do not develop any symptoms until the disease is very advanced. They then become more tired than usual and just start to not feel so good. Their appetite may worsen. When kidney disease gets worse, patients like to keep the room warmer than usual. They often develop anemia.
Symptoms of MKD
The two major characteristics of this disease are (1) slow loss of kidney function and a high serum creatinine level. (2) Usually there is a strong family history, with many affected individuals in the family. Also,
- Patients develop chronic kidney failure with loss of kidney function beginning in the teenage years or twenties and progress to the need for dialysis or kidney transplantation at an age between 30 and 70 years. Patients have few or no other symptoms of kidney disease when they are diagnosed.
Usually, affected individuals are found to have some loss of kidney function when they undergo blood testing by their doctor as part of a general health screening. A blood test called the serum creatinine level is performed. If the blood creatinine level is above 1 mg/dl (US units) or above 88 umol/L (International Units), this is usually abnormal and means the kidney is not removing the creatinine from the blood well enough. In patients with this condition, the serum creatinine is measured by their doctor and is elevated. Frequently the doctor does not know why the serum creatinine level is high. Even if a kidney biopsy (the removal of a small piece of kidney tissue and examination under a microscope) is performed, a correct diagnosis is frequently not made.
- MKD is inherited. If a person has the disease, their children have a 1 out of 2 (50%) chance of having the disease, find out more about Inherited Kidney Disease.
The disease does not skip a generation, though a parent may be less severely affected than their child, and may not have gout or other signs of kidney disease for some time. Almost always, there is at least a parent and child affected with this condition. Frequently, there are many family members affected, including a grandparent, uncles, aunts, cousins, brothers and/or sisters. Sometimes, there are new mutations and only one family member will be affected, but this is rare.
What Can I Do For My Health If I Have MKD?
Currently there is no known treatment for MKD, and the only cure is a kidney transplant. However, there is still a lot that you can do to stay healthy if you have MKD:
- Do not smoke. Smoking makes every type of kidney disease get worse more quickly. It also causes hardening of the arteries and lung disease. The combination of kidney disease and smoking is not good. Thus, it is important to stop smoking if you do smoke. Children of affected MKD patients should be encouraged to never start smoking.
- Check blood pressure regularly. As kidney disease worsens, blood pressure can increase. This rise in blood pressure can lead to a higher risk of heart disease, strokes and heart attacks. If your blood pressure is high, you should get it treated. You should work with your doctor to keep it under good control.
- Stay in shape and keep weight under control. Being very overweight can make it more difficult to do the surgery for a kidney transplant. You should watch your weight closely.
Patient Case
The patient is a young man in overall good health. At the age of seventeen, he was seen by his doctor for general health care. A blood test was done showing that his serum creatinine level was elevated at 1.4 mg/dl in US units (124 umol/L in international units). The patient knew that his father and his grandmother had kidney disease. His grandmother died of kidney failure many years ago, and his father had a kidney transplant and was doing well. He saw a kidney doctor (nephrologist) who was confused as to why there was so much kidney disease in the family. He did a urine test that showed no blood or protein. This was confusing because most patients with kidney disease have blood or protein in the urine. The doctor then did a kidney biopsy, where a small piece of kidney disease is removed. The biopsy showed “interstitial scarring (scarring of the inside of the kidney)”. The biopsy did not have distinctive features that let the doctors diagnose MKD. Thus, the kidney doctor remained uncertain. Later, another doctor suggested that the patient might have MKD. A blood test was sent to the laboratory of Dr. Anthony Bleyer at Wake Forest School of Medicine. The results showed a mutation in the MUC1 gene as a cause of MKD in the patient and his family.
Research
Now that the gene for MKD has been found, a lot of research is being done on this condition. Since there are so few patients with this disease, every patient with the disease who takes part in research provides helpful information. Participating in MKD research trials is also likely to be helpful.
Research Update
We are hoping to begin a clinical trial in the next year to test an already used medicine to see if it helps MKD. Please contact Dr. Anthony Bleyer at kidney@wakehealth.edu for more information.
It was called Type 1 because there are two similar types of this disease. It turns out that the two types of the disease are entirely unrelated.
Like other patients with kidney disease, all patients with MKD should strive to have a kidney transplant done prior to the need for dialysis.
When patients have lost about 2/3 of their kidney function they begin to feel more tired and may develop a decreased appetite.
When 90% of kidney function is lost, patients feel tired and have nausea and usually need a kidney transplant or dialysis.
From this you can see that most of the kidney function has to be lost before any symptoms are noticed. Even then, the symptoms are usually quite mild for a long period of time.