How Common Is IgA Nephropathy by Age, Sex, and Ethnicity?

IgA nephropathy is one of the most common primary glomerular diseases worldwide ^[1]. This means it is a disease that begins directly in the kidneys (primary) and specifically affects the glomeruli, which are the tiny filtering units inside the kidneys. In general, studies suggest that between 25 and 63 out of every 100,000 people have been diagnosed with the condition in Western countries ^[1][2]. It is most frequently diagnosed in adults in their 30s and 40s, though it can occur in childhood or older age ^[3][4]. In many Western countries, men are diagnosed two to three times more often than women ^[4]. However, these numbers vary widely across the globe—it is reported much more frequently in East Asian countries and less often in some populations, such as people of African ancestry ^[5][6]. This variation isn’t just about biology; it is heavily influenced by how different countries screen for and diagnose the disease ^[7].

Understanding the Numbers

The exact number of people who have IgA nephropathy is hard to pin down. Definitive confirmation usually requires a kidney biopsy—a procedure where a small piece of kidney tissue is removed with a needle and examined under a microscope ^[8]. A nephrologist evaluates your specific case, including your urine tests and kidney function, and arranges the procedure if it is safe and appropriate. Because many people have mild forms of the disease that cause no obvious symptoms, they may never be tested or biopsied, meaning the true number of people with the condition is likely higher than reported ^[9].

When researchers look at how many people are diagnosed with the disease (prevalence) or how many new cases are found each year (incidence), the estimates vary significantly depending on where and how the data was collected:

These estimates are heavily shaped by local healthcare practices rather than representing a perfect apples-to-apples comparison of true disease risk ^[13].

Why Does Frequency Vary by Location and Ethnicity?

You may read that IgA nephropathy is most commonly reported in people of East Asian descent, less common in White people (or people of European ancestry), and reported least often in people of African descent ^[6][5]. While this pattern exists in the data, anyone of any ancestry can develop IgA nephropathy. The reported differences are driven by a mix of both biological and healthcare system factors.

Biological Factors

Research shows that genetic susceptibility plays a role ^[7]. The genetic markers associated with the risk of developing IgA nephropathy are found most frequently in East Asian populations, moderately in European populations, and least often in African populations ^[14][15]. However, your ancestry does not determine whether you will get the disease or how your individual condition will behave.

Healthcare System Factors

Differences in healthcare practices are one of the biggest reasons why disease rates vary globally ^[7].

• Urine Screening Programs: In countries like Japan, routine urine screening for school children and workers is standard ^[16]. This practice catches many early, mild cases that might go unnoticed in countries without such programs ^[6]. (The existence of population screening in some countries is not, by itself, a recommendation for everyone to seek it out).
• Biopsy Practices: Because a diagnosis requires a biopsy, countries with different thresholds for when to perform one will report different rates of the disease ^[6]. In Europe, one analysis found a strong association between a country’s overall kidney biopsy rate and its reported incidence of IgA nephropathy ^[13].
• Access to Care: Diagnosing the disease requires access to primary care and specialist referral ^[17]. In areas with limited access to specialized care, or in regions where biopsies are performed less frequently, the disease is likely underdiagnosed ^[18][19].

Age and Sex Differences

Typical Age at Diagnosis

IgA nephropathy can develop at any age, but it is most frequently diagnosed in early to middle adulthood ^[3]. In various medical registries, the average age at the time of biopsy is often between 34 and 46 years old ^[3][20]. The age at which someone is diagnosed is strongly influenced by how they are tested; children may be diagnosed earlier in places with routine pediatric urine checks, while adults may only be identified later when elevated blood pressure (which is often asymptomatic) is noticed or when visible blood appears in the urine (macroscopic hematuria) ^[4]. Being diagnosed outside of this typical age window is not unusual and does not make your diagnosis any less valid.

Why Are Men Diagnosed More Often?

In the United States and Europe, men are diagnosed with IgA nephropathy two to three times more often than women ^[4][20]. However, this is not a universal rule. In Japan, where broad screening catches cases regardless of symptoms, the disease is found at nearly equal rates in men and women ^[12].

This suggests that some of the “male predominance” seen in Western countries might actually reflect differences in how men and women interact with the healthcare system, how severe their symptoms become before seeking care, or different thresholds for doctors recommending a biopsy, rather than a strictly biological difference ^[21][7].

What This Means for You

Epidemiology—the study of how often diseases occur in different groups—helps scientists understand the big picture, but population statistics do not determine your individual journey.

For your own outlook, your care team will track specific clinical factors, including:

• The amount of protein in your urine (proteinuria) ^[22].
• Your kidney filtering function (eGFR), and how it changes over time ^[23].
• Your blood pressure ^[24].
• Relevant findings from your kidney biopsy, such as the Oxford MEST-C score, which grades the amount of inflammation and scarring in the kidney tissue ^[25].

Your prognosis is based on these specific, measurable aspects of your health—not your demographic group alone.