IgA nephropathy (IgAN), also known as Berger’s disease, is considered a rare disease. However, it is the leading cause of kidney inflammation (glomerulonephritis) worldwide. Cases of IgAN appear to be rising, but experts believe this reflects better detection and reporting, rather than an increase in risk.
About 60 out of every 100,000 people worldwide have IgA nephropathy. In the United States, roughly 150,000- 200,000 people have IgAN.
Globally, there are an average of two or three new cases per 100,000 people each year. Rates are the highest in East Asia. Here are the estimated annual new case rates per 100,000 people across several countries and continents:
- Africa: 0.5
- South America: 0.5
- Europe: 1-3
- United States: 2
- Japan: 4.5
Reported rates of IgA nephropathy vary widely by region, but these differences do not always reflect disease risk. Genetics and ethnicity are part of the equation, but how countries screen, diagnose, and track cases strongly shapes the numbers.
Screening Practices
IgA nephropathy appears to be more common in East and Pacific Asian countries, suggesting a higher underlying disease burden in these regions. However, screening practices also influence reported rates.
In countries such as Japan, routine urine testing begins in childhood. This allows healthcare providers to detect kidney changes early and diagnose IgA nephropathy in people with mild or no symptoms. In many other regions, providers do not routinely screen healthy people, so cases often go undetected until a person has symptoms.
Invasive Testing Needed for Confirmation of Diagnosis
A kidney biopsy is the only way to confirm IgAN. A kidney biopsy is when providers use a needle to remove a piece of kidney tissue for examination under a microscope. Because biopsies are invasive and not always available, many people never receive a formal diagnosis. Milder cases are often missed, while more severe cases are more likely to appear in official statistics.
The Way Researchers Measure Rates
Some researchers track incidence, which is the number of new diagnoses each year. Others measure prevalence, or the number of people who live with the disease. Estimating these numbers is difficult because many people have no symptoms, a diagnosis requires a kidney biopsy, and screening and access to care vary.
Many gather data from kidney biopsy registries, national databases, or insurance claims. These sources reflect who gets tested and diagnosed but don’t reflect everyone who has the disease. As a result, lower reported rates in regions such as South Africa may reflect underdiagnosis rather than lower risk.
Research and Healthcare Gaps
Most studies focus on Asia, Europe, and North America. Very little data exist from Africa or from Black, Hispanic, and Latino populations. These gaps limit what researchers can conclude and highlight the need for larger, more diverse studies with equal access to kidney testing.
Anyone can develop IgA nephropathy, but the likelihood varies based on:
- Ethnicity: IgAN is most common in people of Asian ancestry.
- Gender: Men have a two- to three-times higher risk in North America and Europe, but the risk is similar between genders in Asian populations.
- Age: IgAN is more common in people aged 10-40.
- Genetics: IgAN isn’t passed down like eye color. However, if you have genetic variations in the HLA region (and some other genes), you have a higher risk of developing IgAN. Having these genes does not mean you will develop the disease, as this accounts for less than 10% of your risk.
- Family history: Most cases of IgAN occur randomly without any family history. Fewer than 1 in 10 people with IgAN have a close relative with it. However, sometimes the abnormal IgA (the antibody that clumps up and causes problems) does run in families. About 1 in 4 close relatives might have higher levels of this abnormal IgA in their blood, but most of them never develop kidney disease.
- Lifestyle factors: Some lifestyle choices can be especially hard on your kidneys, raising your risk. For example, high blood pressure and smoking damage the blood vessels in your kidneys, and carrying extra weight makes your kidneys work harder.
- Infections and health conditions: Symptoms of IgA nephropathy often flare after infections, especially colds, sore throats, or respiratory infections. These infections don’t cause the disease, but they can trigger immune responses that cause or worsen symptoms. IgA nephropathy also appears more often alongside certain health conditions, including autoimmune conditions and liver disease.
Contact a healthcare provider if you notice symptoms of IgAN, such as:
- Dark, pink, red, or cola-colored urine
- Foamy urine
- Swelling in your face, hands, feet, or ankles
- Fatigue or headaches that don’t improve
- Abdominal pain
Your provider may use risk assessment tools that combine lab results, blood pressure, and medical history. If you are at high risk, they may periodically check your urine for protein and monitor your kidney function through blood tests.
