FAQs

C3G and primary IC-MPGN are two different ultra-rare kidney diseases that share a common issue: an overactive C3 protein in the immune system. Normally, C3 helps protect the body from infections, but when it becomes overactive, it can mistakenly damage the kidneys. This happens by affecting the glomeruli - the tiny filters in the kidneys responsible for removing waste and excess fluid.

Despite being distinct conditions, C3G and primary IC-MPGN have overlapping signs and symptoms, including the triad of:¹

• Proteinuria (high levels of protein in the urine)
• Reduced kidney function
• C3 deposits in the kidney

While C3G and primary IC-MPGN are similar, they are caused by different underlying processes in the body. Finding these differences in a biopsy helps your doctor provide an accurate diagnosis so that together you can choose the best care plan for you.

C3G^1,2 occurs when an abnormal amount of the C3 protein is found in the kidneys without significant antibody accumulation.

Primary IC-MPGN ¹ occurs when both C3 and antibodies build up in the kidneys.

These conditions can affect anyone, but they are most commonly diagnosed in childhood or early adulthood. They affect males and females equally, and in most cases, there is no clear reason why they develop. However, some people may have a higher risk if they have:¹

• A family history of kidney disease
• Certain genetic factors that affect how their immune system and kidneys work
  
  While certain factors may contribute to disease development, these are not things you could have controlled or prevented.

Both C3G and primary IC-MPGN disrupt the kidney’s ability to filter blood effectively, leading to similar signs and symptoms:¹

• Proteinuria: Excess protein in the urine
• Swelling (oedema): Fluid retention, particularly in the legs, ankles, hands, and around the eyes
• Hypertension (high blood pressure): A common symptom that can worsen kidney damage over time
• Haematuria (blood in the urine): Urine may appear pink, red or brown or microscopic blood may be detected during testing
• Fatigue and weakness: Caused by the build-up of waste products in the blood and sometimes worsened by anaemia
• Decreased kidney function: Often identified through blood tests, such as elevated creatinine and reduced eGFR levels, and can progress to kidney failure in severe cases

It’s important to note that symptoms can vary depending on the stage of the disease and any underlying conditions that might be contributing to the kidney damage.

People showing signs and symptoms of kidney dysfunction may be asked to go through a range of diagnostic procedures. This may feel like a lot of tests, but they are essential for getting a clear and accurate diagnosis. Some patients may feel anxious about a kidney biopsy, which is a common response to an invasive test, but it is the only reliable way to confirm whether you have C3G or primary IC-MPGN.³ Having this clarity ensures you receive the right care plan tailored to your needs.

Tests may include:

• Medical history and physical examination: to assess symptoms, family history, and underlying conditions.
• Urine and blood tests: to check for proteinuria (protein in urine) and haematuria (blood in urine).
• Kidney biopsy: to look at structural changes in the kidney and identify deposits.
• Genetic and complement tests: to find abnormalities in the complement system that may drive kidney damage.

Your healthcare team will regularly monitor your condition to track how the disease is behaving and to see whether treatments are working effectively. Monitoring usually includes:

• Blood tests to check kidney function.
• Urine tests to measure proteinuria and haematuria.
• Blood pressure checks, since high blood pressure can cause or worsen kidney disease.

For C3G, complement system tests (C3, C4, factor H, and sometimes genetic testing) are particularly important because they can give clues about how the disease is progressing.

Both C3G and primary IC-MPGN are chronic progressive diseases. Many people may experience declining kidney function, and some may eventually reach kidney failure (end-stage kidney disease). Early diagnosis, close monitoring and timely treatment allow your healthcare team to create an individualised care plan, which can help delay or sometimes prevent the need for dialysis or a kidney transplant.⁴

Here are some suggestions to help you to feel more in control of your condition:
Speak to your healthcare provider about any dietary adjustments you can make and what physical activity might be best for you.

• Take care of your emotional well-being by talking to family or friends. You can also contact your local patient organisation. If you feel you need more emotional support or want to learn new coping skills, explore your options for speaking to a trained counsellor or a patient support group.
• Schedule regular follow-ups with your nephrologist, ensuring you discuss any new signs, symptoms or concerns you might have. That’s what they are there for!

When managing your kidney health in the presence of C3G or primary IC-MPGN, it is vital that you eat well.

A kidney-friendly diet consists of fresh whole foods that are limited in salt,⁵ provide a moderate amount of high-quality protein,⁶ and support hydration.⁷ Depending on your stage of chronic kidney disease, you might also need to limit potassium and phosphorus, as when imbalanced they could affect your overall health.⁸ Eating fresh whole foods and limiting processed food, additives, and hidden salts can ease the workload on your kidneys, assist in managing blood pressure,⁵ and help to reduce swelling in your body.

Since each person is unique, it is critical that you obtain individualised advice from a medical provider or dietitian to help you create a nutrition plan that is safe, beneficial and enjoyable for you.

It’s a good idea to prepare for appointments with your nephrologist. You can ask the questions that are relevant to you, to help you understand your condition better.

For tips on preparing for your next appointment take a look at our patient guide.

While C3G and primary IC-MPGN mainly affect the kidneys, they can also impact hormonal balance, menstrual cycles, and reproductive health. Women with chronic kidney disease often experience irregular periods and reduced ovarian reserve.⁴

These changes may make conceiving harder.⁹ So, it’s important to speak to your healthcare team and be open and honest about your fertility considerations – now and in the future. Your nephrologist will be able to ensure that you are on the right care plan and can refer you to a reproductive specialist if required.  

Children with C3G or primary IC-MPGN may experience slowed growth (height, weight, BMI) and variations in development.¹⁰ Regular monitoring and supportive care, including dietary guidance, can help optimise outcomes and support achievement of developmental milestones.

Educational and social development may also be affected. Frequent medical appointments, fatigue or time off school can impact academic success, social engagement and psychological development.

Importantly, many children are still able to grow and develop well, with outcomes varying depending on how early the disease is diagnosed, how well it is controlled, and the supports put in place.

Living with chronic kidney disease affects more than just your physical health, it can bring emotional challenges too.

It’s important to talk about how you’re feeling. Whether it's with your healthcare team, loved ones or others who understand what you’re going through, connecting with others and sharing your feelings can make a big difference. There are many support options available, and a wide range of organisations to offer guidance, comfort and practical help.

If you notice changes in your emotional wellbeing, share these with your healthcare team. Your emotional health matters just as much as your physical health.

Living with a rare kidney disease can affect daily routines at school or work. Fatigue, frequent appointments and hospital stays can make it harder to keep up, build connections or balance health with other responsibilities.

Schools may be able to help by offering learning plans or special accommodations that allow students to stay on track while managing their health. Workplaces can often provide support too, such as through flexible hours, remote working, or small adjustments that make it easier to balance work and treatment.

Having open, proactive conversations with teachers, employers or human resources teams can help build understanding and may uncover support that already exists. Patient organisations can also help you understand your rights and point you to resources that support you in education and at work.

You can learn more about your condition by looking at these websites:

• World Kidney Day: worldkidneyday.org
• Nephcure: nephcure.org
• Compcure: Compcure.org
  
  You may find it helpful to connect with others who share your specific challenges and can offer comfort and encouragement. Patient support groups are available online, including social media groups. 
  
  It’s also important to communicate openly with your healthcare team - ask questions, share your concerns and discuss your thoughts to ensure the care you receive is meeting your needs.

Caregivers can play a vital role in supporting someone living with rare kidney disease. Ways in which you can help include:

• Tracking symptoms
• Keeping on top of appointments, helping to ensure that appointments are attended, help to prepare a list of questions for the nephrologist and take notes from the appointment
• Providing emotional support
• Encouraging adherence to care plans