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Dense deposit disease (DDD) is an extremely rare kidney disease affecting fewer than 5,000 people in the United States. DDD damages the kidneys’ filters over time, and many people eventually develop kidney failure. When living with a rare disease like DDD, it helps to learn as much as you can to lead a healthier life.
This article covers five facts about DDD. It touches on the disease’s causes, symptoms, and how doctors diagnose it. We’ll also discuss how DDD treatments focus on slowing kidney damage and controlling symptoms.
DDD is a rare kidney disease that falls under the category of complement 3 glomerulopathy (C3G). The other type of C3G is called C3 glomerulonephritis (C3GN). Both types of C3G affect the kidneys’ glomeruli. Glomeruli are delicate filters that remove waste and toxins from the blood to make urine. Doctors tell DDD apart from C3GN based on how the kidney tissue looks under a microscope.
People with DDD have an overactive complement system. This part of the immune system acts as a first line of defense against infection. Proteins normally act like brakes to keep it under control until it’s needed. In DDD, the brakes fail, and the system becomes too active. When activated, complement protein 3 (C3) breaks into smaller fragments. Too many of these fragments build up in the glomeruli, causing inflammation that damages the kidneys’ filters.
DDD and C3GN are two types of the same disease group, called C3 glomerulopathy. The main difference is how the kidney tissue looks under a microscope. In DDD, the clumps are very dense and sit in one layer of the kidney filter. In C3GN, the clumps are in different spots and look less dense.
Doctors and researchers have found that DDD has two main causes. It can be caused by immune system proteins that target the complement system, or it can be caused by genetic mutations (changes) that affect complement proteins. Both causes take away the “brakes” and eventually lead to kidney damage.
Some people with DDD have abnormal antibodies called nephritic factors (NeFs). Antibodies are immune system proteins that protect you from infections. Some antibodies, called autoantibodies, mistakenly attack healthy tissue instead of harmful germs.
NeFs are autoantibodies that target complement factor H (CFH). Factor H normally helps keep the complement system turned off until it’s needed. When NeFs interfere, the system stays switched on, which sets off a chain of reactions that overactivate the system and damage the kidneys. Research shows that around 80 percent of people with DDD have C3 nephritic factor (C3NeF) activity.
Genes provide instructions for making proteins, like recipes in a cookbook. A mutation is like a misprint in the recipe — the final dish doesn’t turn out right. Studies have found that mutations in the CFH gene also lead to complement system dysregulation (faulty proteins). Some cases of DDD develop from CFH gene mutations.
DDD symptoms tend to start earlier in life, usually when people are teenagers. However, some people may not notice any signs until they’re adults.
Most people with DDD have blood or protein in their urine. Healthy glomeruli normally stop large molecules — like proteins and blood cells — from getting into urine. Some people have dark, foamy urine as a sign of proteinuria or protein in their urine. Red, brown, or pink pee may be due to hematuria, or blood in the urine.
When too much protein leaks into the urine, it upsets the body’s fluid balance. Low protein levels force fluid out of the bloodstream and into nearby tissues. This causes swelling or edema. Signs of DDD include swelling in the ankles and feet.
Another symptom of kidney disease is hypertension (high blood pressure). Around half of those with DDD have high blood pressure. Hypertension is common in kidney diseases because the kidneys play a key role in controlling blood pressure levels. Damaged kidneys can’t remove extra fluid, so it builds up in the body. This fluid puts added pressure on the blood vessels.
People with DDD can also develop drusen (clumps of proteins and fats) in their eyes. These deposits form in the retina (the light-sensitive tissue in the center of the eye). Most cases of drusen don’t cause any symptoms. Eye doctors usually find them during routine eye exams.
Partial lipodystrophy refers to an abnormal distribution of fat tissue in the body. You may be at risk for this condition if you have DDD. Some people develop partial lipodystrophy before or after their DDD diagnosis. The fat loss may affect the abdomen, upper body, face, and arms. Researchers think partial lipodystrophy is due to the complement system destroying fat cells.
If you begin experiencing symptoms of DDD, make an appointment with your doctor. They’ll likely refer you to a nephrologist. Nephrologists are specially trained to diagnose and treat rare kidney diseases like DDD.
Blood and urine tests check for abnormalities associated with DDD. Urine tests look for blood cells and abnormally high protein levels in urine.
Using a small blood sample, doctors can measure your complement protein levels. Low C3 with normal C4 is common in DDD/C3G and supports the diagnosis, but a kidney biopsy is needed to confirm it. Blood tests check for waste products that accumulate in the body, such as creatinine and urea, as well as any imbalances in electrolyte levels. Blood tests also check your estimated glomerular filtration rate (eGFR). This is a measure of how well your kidneys filter blood, and the values show how severe the kidney damage is.
If urine tests show that you have proteinuria and hematuria, your doctor will order more testing. Kidney biopsies are a key part of diagnosing C3G. Your nephrologist or a radiologist will use a thin needle to take a small tissue sample from your kidney. The sample is sent to a lab for closer inspection.
Immunofluorescence uses special dyes that attach to specific proteins. When the sample is looked at under a special microscope, tissue specialists can see where the proteins are. Pictures of DDD using immunofluorescence show deposits or clumps of C3 proteins stuck in the kidneys.
Electron microscopy uses powerful microscopes to magnify images thousands of times. Tissue samples from people with DDD show sausage-shaped or ribbonlike C3 deposits. These pictures help doctors tell the difference between DDD and C3GN. C3 deposits in C3GN usually form in different parts of the kidney compared to DDD.
Unfortunately, around 50 percent of people with DDD develop kidney failure within 10 years of their diagnosis. After 20 years, that number increases to 85 percent. Working closely with your nephrologist and following your treatment plan can help slow DDD progression and delay kidney failure.
Until recently, there weren’t any DDD treatments approved by the U.S. Food and Drug Administration (FDA). In 2025, the FDA approved two medications for DDD. These are the first medicines made just for this disease. The first one, called iptacopan (Fabhalta), was approved in March. The second one, called pegcetacoplan (Empaveli), was approved in July for people 12 and older. Iptacopan is taken orally, while pegcetacoplan is given as a subcutaneous (under the skin) injection, usually twice a week. Pegcetacoplan is also approved for another complement-mediated kidney disease, IC-MPGN.
Both medications are known as complement inhibitors. They work by calming down part of the immune system called the complement system. In people with DDD, this system becomes too active and damages the kidneys. These drugs help stop that damage by blocking the overactive immune response.
Other treatments for DDD focus on treating symptoms like high blood pressure and proteinuria. If you’ve been diagnosed with DDD, the first treatment you may have been given is a blood pressure medication. These drugs lower the amount of protein lost in your urine. Examples include:
Corticosteroids (steroids) and immunosuppressive drugs help calm inflammation to protect the kidneys. Treatment depends on how severe your disease is. An example of an immunosuppressant used for DDD is mycophenolate mofetil (MMF). Your doctor may prescribe MMF alone or with a steroid.
In people who develop kidney failure, dialysis and kidney transplants are an option. If you have a kidney transplant, DDD often comes back. About half of transplants in people with DDD eventually fail within 10 years because the disease returns. Even with these challenges, progress is being made. New treatment options are offering hope, and working closely with your care team can help you protect your health.
On MyKidneyDiseaseTeam, people share their experiences with kidney disease, get advice, and find support from others who understand.
Are you living with dense deposit disease? Let others know in the comments below.
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