The U.S. Food and Drug Administration (FDA) defines rare kidney diseases as conditions that affect fewer than 200,000 people. While these diseases aren’t as common as chronic kidney disease (CKD), they share many of the same signs. There are more than 150 types of rare kidney diseases, meaning there’s a range of symptoms.

This article covers eight symptoms of rare kidney disease — including complement 3 glomerulopathy (C3G) and immune complex membranoproliferative glomerulonephritis (IC-MPGN). To learn more about rare kidney diseases and their symptoms, talk to your doctor or nephrologist (kidney specialist).

1. Urine Changes

One of the most obvious signs of any form of kidney disease is changes in your urine. After you use the bathroom, take a look at your urine. Is it yellow and clear? Or is it foamy, dark, or cloudy? These may be signs of kidney disease and damage.

In a healthy, well-hydrated person, urine is typically clear to light yellow. If you notice a pink or red tinge, you may have hematuria (blood in your urine). These colors are a sign of kidney damage. Your kidneys’ filtering units — or glomeruli — normally stop larger substances from leaving the body. Damaged glomeruli let red blood cells (RBCs) through, giving your urine a darker appearance. Hematuria is a sign of both C3G and IC-MPGN.

Sometimes, you can’t see blood in your urine with the naked eye. This is known as microscopic hematuria. If your doctor thinks you have kidney damage, they’ll look at a urine sample under a microscope.

Foamy urine is also a sign of rare kidney disease. There’s a chance you have protein in your urine (proteinuria). Like RBCs, proteins can leak into your urine due to damaged glomeruli. The National Kidney Foundation explains that foamy urine can look like foam created when scrambling eggs. Bubbles or foam that hang around in the toilet after flushing several times is also a sign of proteinuria.

Getting up to go to the bathroom in the middle of the night is a nuisance. But did you know it may be a sign of rare kidney disease? In the early stages, kidney damage can make you feel like you have to urinate more than usual. Frequent nighttime urination can also point to other health problems. Talk to your doctor about other causes — like an enlarged prostate or urinary tract infections.

2. Swelling

The kidneys constantly filter blood to remove extra water and waste. These organs also help balance your fluid and salt levels. Normally, your kidneys get rid of excess fluid by turning it into urine. If you need to hold on to fluid to raise your blood pressure levels, your kidneys raise your sodium levels.

Kidney damage from rare kidney diseases causes your body to hang on to more sodium. Because salt retains fluid, you also increase your fluid levels. The extra fluid has nowhere to go, so it starts collecting in your feet, ankles, and hands. The skin around your eyes may also become puffy. Edema (swelling) is a common sign of kidney disease — including C3G and IC-MPGN.

3. Neurological Symptoms

If you’ve had a harder time concentrating or fighting fatigue, your brain may not be to blame. Rare kidney diseases can also cause these symptoms. Damaged kidneys can’t properly filter waste products and toxins. They eventually build up in your bloodstream and begin affecting your brain. People with kidney diseases like C3G can experience confusion, difficulty concentrating, or extreme tiredness. You may also have headaches and trouble sleeping.

4. High Blood Pressure

Your kidneys play a key role in regulating your blood pressure levels through controlling fluid levels. The more fluid there is in your body, the harder your heart needs to beat to push it through your arteries. Blood pressure is the measurement of the force exerted on these arteries when your heart beats and relaxes.

People with rare kidney diseases usually have hypertension (high blood pressure) from fluid buildup. If it’s left untreated, hypertension can damage the kidneys even more. You likely won’t notice any symptoms of hypertension. Some people with hypertension have headaches. Be sure to talk to your healthcare provider about ways to manage high blood pressure.

5. Changes in Your Oral Health

Kidney disease can affect your oral health and sense of taste. Researchers believe toxin buildup in your bloodstream is to blame for these changes. For example, extra waste products — like urea, made when the body breaks down protein — can collect and make your saliva taste bitter. High blood sodium levels make it harder for you to taste salt in your food. Other changes you may notice include the following:

• Little to no taste when eating or drinking
• A metallic taste in your mouth
• Dry mouth

Inflammation from rare kidney diseases affects your immune system’s ability to fight infections. This is especially true for bacterial infections in your mouth. It’s vital to take good care of your teeth and oral health to prevent cavities. Bacteria from gum disease and cavities can spread throughout your body, raising your risk of serious infections.

6. Gout

Gout is a type of arthritis caused by the buildup of uric acid in your joints. Uric acid is a waste product made when you break down certain chemicals from your diet. Your kidneys normally filter uric acid out into your urine. However, damaged kidneys can’t filter out enough acid, so it collects in your bloodstream.

Uric acid eventually forms crystals in joints throughout the body, especially in the big toe. People with gout usually experience pain, swelling, and stiffness in the affected joint. Gout symptoms come and go in attacks that can last a few weeks at a time.

7. Increased Risk of Infections

Some rare kidney diseases develop from issues with the immune system. This makes it harder for your body to fight off viral and bacterial infections. For example, C3G affects the complement system. This complex system normally attacks and destroys bacteria and infected cells. C3G uses up the complement proteins, so they can’t fight infections as well as they should.

Doctors and researchers think this is why people with C3G have more infections than those without. If you’re getting sick more often than normal, it may be a sign of a rare kidney disease.

8. Other Symptoms Associated With Rare Kidney Diseases

Rare kidney diseases affect more than just your kidneys. Other organs are also at risk of damage. In the case of C3G, complement system proteins harm the eyes and fat tissue. You may notice changes in your vision or fat distribution throughout your body.

As your kidney disease progresses, you may eventually develop kidney failure. Signs that your kidneys no longer work as well as they should include:

• Itching due to a chemical imbalance in your blood
• Changing appetite
• Urinating more than usual in the early stages of kidney disease and less as kidney damage progresses
• Cramping muscles from electrolyte imbalances, often due to low calcium

What Are the Next Steps?

If you’re experiencing any symptoms of kidney disease, make an appointment with your doctor. They’ll order diagnostic tests to check your kidney function. This can include blood and urine tests (urinalysis). If the standard tests don’t show the cause of kidney disease, which happens in cases of rare kidney conditions, they’ll do additional tests to figure out the cause. Once you receive your diagnosis, it’s important to start treatment to avoid further kidney problems.

Talk With Others Who Understand

On MyKidneyDiseaseTeam, the online social network for people with kidney disease and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with kidney disease.

Are you living with a rare kidney disease? What symptoms did you experience before your diagnosis? Share your story in the comments below, or start a conversation by posting on your Activities page.