Dense deposit disease (DDD), also called membranoproliferative glomerulonephritis type II or MPGN II, is a rare autoimmune disease that affects the kidneys and the eyes. As the name MPGN II implies, DDD damages the glomeruli within the kidneys. Proteins that are part of the immune system attack and stick to the glomerular basement membrane in thick patches that are called dense deposits. Over time, these deposits interfere with the kidneys’ ability to filter fluids and wastes from the blood. About half of the people affected will progress to kidney failure within 10 years of being diagnosed and 85% will develop kidney failure within 20 years. Deposits in the retina of the eye appear whitish-yellow and are called drusen.
DDD is often diagnosed in children and teenagers between the ages of 5 and 15 years. This extremely rare disease affects only two or three people in every million.
DDD is an autoimmune disease. A normally functioning immune system differentiates between foreign invaders and the body’s own cells. It destroys bacteria and viruses, triggers inflammation and removes debris from cells and tissues. An autoimmune disease causes the immune system to no longer make this distinction and attacks the body’s own organs and tissues. In some people with DDD, mutations have been found in the complement factor H (CFH) gene which makes complement factor H protein to help regulate part of the body’s immune system. Because of the gene mutations, this protein is defective, causing an overactive immune system that attacks the kidneys. However, not everyone with gene mutations develops DDD. Other unknown factors such as certain medications, chronic diseases, infections, cancers and pregnancy may play a vital role.
Since DDD affects the kidneys first, early symptoms resemble those of kidney disease and include protein in the urine (proteinuria), which makes it appear foamy, and pink-tinged or red urine caused by blood (hematuria).
As kidney disease progresses, symptoms become more noticeable:
DDD is diagnosed with a kidney biopsy. A small amount of kidney tissue is examined under an electron microscope, which reveals the dense deposits. Blood tests for nephritic factors — autoantibodies that interfere with the proper functioning of the immune system — can also be done.
As kidney disease progresses to kidney failure, all major organs are affected. Complications include heart disease, bone disease, gastro-intestinal disturbances, nervous system problems such as peripheral neuropathy and restless leg syndrome (RLS), dry skin and itching, anemia, high blood pressure and a decreased ability to fight infections.
Drusen deposits in the eyes usually occur in people who have had DDD for 20 years or more. Drusen may cause colorblindness, night vision impairment and loss of vision.
Like all autoimmune diseases, DDD is not curable. However, treatments are available to slow the progression of kidney disease and treat kidney failure once it occurs. Treatments include:
There is no current treatment for drusen, but some of the same therapies used in age-related macular degeneration (AMD), a disease that destroys vision, can be helpful. People with DDD should see an ophthalmologist (a medical doctor who specializes in eye care) regularly.
Ongoing research into the causes and treatment of DDD focuses on the role played by the faulty complement factor H protein, development of a specific immunotherapy, restoration of factor H production through bone marrow transplantation, and others. Kidneeds, a fund of the Greater Cedar Rapids Community Foundation, is a non-profit organization that raises funds exclusively for DDD/MPGN II research. DDD patients can participate in an ongoing research survey at the organization’s website and read about other continuing studies.
Though DDD is a rare autoimmune disorder, organizations like Kidneeds are raising awareness to help those who do live with it. Usually diagnosed in childhood, DDD affects the kidneys and oftentimes the eyes. Although there is no cure for DDD, treatments are available to slow the progression of kidney disease.
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