Complement 3 glomerulopathy (C3 glomerulopathy) is a very rare kidney disease. Those diagnosed with it have one of two forms of this disease: dense deposit disease (DDD) or C3 glomerulonephritis (C3GN). Both result from a problem with a specific part of the immune system called the alternative complement pathway.
Both types of C3 glomerulopathy can cause significant kidney disease and have a major effect on your health.
How the Complement System Affects Your Kidneys
When you have C3 glomerulopathy, your alternative complement system is overactive. When it reaches this state of high alert, it starts to break down proteins in your body called complement 3 (C3) proteins when it shouldn’t.
C3 proteins are blood proteins that play an important role in your immune system. When the complement system breaks them down unnecessarily, they go into your kidneys. Once there, they cause inflammation that damages your kidney filters, called glomeruli.
You have about a million glomeruli in each of your kidneys. Their job is to filter your blood and allow smaller molecules, wastes, and water to pass into tiny structures called tubules. These remove excess acid and return needed substances to the blood such as water, minerals, and other nutrients. The remaining fluid and wastes become urine, which you pee out.
When glomeruli are damaged, they can’t filter blood very well, and toxins build up in your blood.
As C3 glomerulopathy gets worse, the kidneys find it more difficult to do their job. This means it will become harder for them to:
- Remove waste from your body
- Balance your body’s fluids and electrolytes
- Regulate your blood pressure
- Make hormones that help create red blood cells
But you may not notice any symptoms of these problems until you start to lose kidney function.
When C3 Glomerulopathy Damages the Kidneys
Once you begin to lose kidney function, you may notice the following:
Blood in your urine. It may be pink, red, or brown. This is because the damaged glomeruli leak red blood cells into your pee.
Extra protein in your urine. Like blood, protein can leak into your pee, too. You may notice that your urine looks foamy, cloudy, or dark.
Less urine. Since your kidneys aren’t filtering the way they used to, you may notice that you go to the bathroom less frequently.
Swelling of your hands, feet, and ankles. With kidney disease, there is loss of a blood protein called albumin in the urine, which makes you less able to get rid of salt and water. This causes fluid to build up in your body and can cause puffiness in your hands, feet, ankles, and sometimes around your eyes.
Gout. Since your kidneys can’t filter out uric acid, it builds up in your blood and sometimes in your joints, which causes this type of arthritis.
High blood pressure. Reduced kidney function causes fluid buildup, which puts more pressure on the blood in your arteries and raises blood pressure.
Fatigue. Waste accumulates in your blood, which can affect your brain. You may feel more tired or have trouble focusing.
Kidney damage from C3 glomerulopathy occurs slowly over time. But after about a decade, around half of all people with the condition have kidney failure. Symptoms of kidney failure include:
- Loss of appetite
- Nausea and vomiting
- Trouble sleeping
- Dry, itchy skin
- Nighttime muscle cramps
How to Manage C3 Glomerulopathy and Prevent More Kidney Damage
You most likely cannot reverse kidney damage from C3 glomerulopathy, but you can do things to help prevent kidney disease from worsening. Your doctor may recommend the following:
Blood pressure medications. Two types of drugs, ACE inhibitors and ARBs, help reduce the leaking of protein into your urine.
SGLT-1 inhibitors. These meds lower your blood sugar by allowing your kidneys to remove sugar from your body through your pee.
Sparsentan (Filspari). This medicine helps lower the protein in your pee and may be given if you're at high risk of your C3G getting worse.
Mycophenolate mofetil (MMF). This medicine calms the immune system and may help prevent kidney disease from progressing to kidney failure.
Eculizumab. If your C3 glomerulopathy doesn’t respond to other medications, your doctor may recommend this drug. It is a monoclonal antibody that specifically targets the complement system. Research suggests it can decrease protein in the urine and slow down the progression of kidney disease in some, but not all, patients. People with C3 glomerulopathy who have high levels of a substance called soluble C5b-9 are most likely to benefit from this medicine.
Lifestyle changes. Several lifestyle changes may slow the disease's progression. These include:
- A low-salt, low-protein diet
- Maintaining a healthy weight
- Controlling your blood pressure with diet and medications
- Taking cholesterol-lowering medications
- Stopping smoking
Sometimes, people with C3 glomerulopathy don’t respond to any of these treatments. In this case, they will slowly worsen until they go into kidney failure. At that point, they may require dialysis. This is a repeated procedure in which a machine does the work of cleaning the blood that the kidneys can no longer do. Some people need a kidney transplant to stay alive. It’s hard to know who will get to that point and who will respond to treatment. But since there is no cure for C3 glomerulopathy, it’s important to follow the treatment plan recommended by your health care team carefully.
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SOURCES:
National Kidney Foundation: “Treatment for C3G,” “Complement 3 glomerulopathy: Knowing the Signs and Symptoms,” “Complement 3 Glomerulopathy.”
National Organization for Rare Disorders: “C3 Glomerulopathy: Dense Deposit Disease and C3 Glomerulonephritis.”
National Institute of Diabetes and Digestive and Kidney Diseases: “Glomerular Diseases.”
