Questions and answers about DDD
Q: What is DDD?
A: DDD stand for Dense Deposit Disease. It used to be called membranoproliferative glomerulonephritis type II. It is a kidney disorder that stops the kidneys from correctly filtering waste from the blood. The immune system of persons with DDD does not work correctly and deposits to build up in the kidneys. These deposits are located in the filtering part of the kidney, which is known as the glomerulus. Glomeruli become inflamed and their ability to filter and clean the blood is destroyed. For more on how your kidneys work and what happens when they don’t, click here.
Q: How is DDD diagnosed?
A: To find out if you have DDDI you need to have a kidney biopsy. Your doctor will take a small amount of tissue from your kidneys and look at it under an electron microscope to see if there are dense deposits. The disease gets its name from these deposits. The deposits are seen best with an electron microscope, so electron microscopy will be done on the biopsy tissue.
Q: What causes DDD?
A: DDD is caused by uncontrolled activity of the alternative pathway of the complement cascade. In a few persons with DDD, disease-causing mutations can be found in complement genes.
Q: What is the complement cascade?
A: The complement cascade is a part of the immune system that helps the body fight infections. The complement group of proteins assists in killing bacteria, viruses or infected cells. The complement cascade is like a chain reaction that causes an attack on infected cells. The alternative pathway is one of three different complement pathways that are known.
Q: Why is uncontrolled activation of the complement cascade so bad?
A: Uncontrolled activity of the alternative pathway of complement means that the alternative pathway is constantly on and is running unchecked and out of control. Normally, the alternative pathway should defend the body from an invader but when the alternative pathway is out of control, it does not know when to stop. It will attack both infections and the body. In DDD, the kidneys are damaged. The eyes can be damaged as well.
Q: What happens to someone with DDD?
A: About half of people with DDD progress to kidney failure over time. If you go into kidney failure, your kidneys don’t work well enough to keep you alive. You need dialysis or a kidney transplant to live. Different studies report different statistics about the amount of time that it takes for a person with the diagnosis of DDD to go into kidney failure. In about half of people diagnosed with DDD, their kidneys fail in 8-12 years; in 85% of people, their kidneys fail within 20 years (50% Habib et al. (1987); 67% Davis, et al (1978); 11% McEnery et al. (1980) 61% Cameron(1982); 76% Schwertz, et al(1996)).
Q: What is the current treatment for DDD?
A: There is currently no treatment that is specific for DDD, however there are promising drugs on the horizon. There are also standard (general) ways to treat people who are developing kidney disease, and you should discuss these treatment options with your doctor.
Q: Can you get a transplant if you have DDD?
A: Yes, you can get a kidney transplant. In most cases, DDD recurs in the transplanted kidney. Eddy et al (1984) reports that 5 of 10 transplanted kidneys were lost due to recurrent DDD between 9 months and 8 years following transplantation in 4 of 6 individuals. These figures suggest that half of the transplanted kidneys eventually fail due to recurrent disease.
Q: When should a transplant be done?
A: This decision should be made by you and your physician. Although there is a high risk of recurrence, some people do well for several years. You need to weigh how you are doing on dialysis, the waiting period on the transplant list or availability of a living donor, and your quality of life. Transplantation also has problems, and those need to be considered when you are deciding whether to transplant or stay on dialysis.
Q: I have heard that DDD also affects the eyes. What happens?
A: Deposits similar to the deposits found in the kidney can be found in the eye. These deposits are called drusen. The amount of drusen is not related to disease activity. Some people who go into kidney failure quickly have no drusen, and some who have no kidney problems have drusen. The amount of drusen a person has does seem to be related to the amount of time they have had DDD, and so drusen are more likely to be found in persons who have had DDD for a long time. Some studies have suggested that after about 20 years, drusen may cause problems with color discrimination, night vision and occasionally, loss of vision. Although there is no current treatment for drusen, people with DDD should be followed by an ophthalmologist. New therapies are now being tried in adults with age-related macular degeneration (AMD). AMD is very similar to the drusen in DDD and so the same therapies may be helpful for persons with DDD.
Q: Is DDD a genetic disease?
A: Persons with DDD have a complex genetic disease. Persons can inherit a predisposition to developing DDD. However genes are not the only factor that leads to the development of DDD. There are additional trigger(s) that start the disease process, but we do not know what these triggers are.
Information provided by Richard J.H. Smith, MD.
Last updated 8/14/14