What Causes IgA Nephropathy? Genetic or Contagious?

Summary: The exact cause of IgA nephropathy is not fully known. It is an immune-mediated kidney disease involving genetic susceptibility and other complex factors. It is not contagious, and it is not caused by a personal failing or everyday lifestyle choice.

When you are diagnosed with a chronic condition like Immunoglobulin A (IgA) nephropathy, it is completely normal to wonder, “Why did I get this? Did I catch it? Did I pass it to my kids? Did I do something wrong?”

The short answer is: No, you did not do anything to cause your IgA nephropathy, and it is not contagious ^[1]. You cannot pass it to someone by spending time with them, and you did not get it because of your diet or everyday lifestyle choices ^[2][3]. IgA nephropathy is an immune-mediated kidney disease where your body’s defense system behaves abnormally ^[1]. While genetics play a role in making some people more susceptible, it is usually not a single-gene inherited disorder that will automatically be passed down to your children ^[4][5].

Here is what the medical research tells us about the current understanding of how and why IgA nephropathy happens.

The “Four-Hit” Model: An Immune System Mix-Up

To explain what happens in IgA nephropathy, researchers currently use a framework called the “four-hit model” ^[1][6]. This is a proposed model of the disease biology, rather than a completely proven explanation for every single patient:

1. Altered Antibodies: Your immune system makes an antibody called Immunoglobulin A (IgA) to fight off infections. In IgA nephropathy, your body may produce an altered version of this antibody, called galactose-deficient IgA1 ^[1]. This simply means the antibody has fewer galactose sugar molecules attached to it than usual.
2. The Body Reacts: Your immune system may not recognize this altered IgA as normal, so it creates other antibodies to attach to it ^[1].
3. Clumping Together: The attacking antibodies bind to the altered IgA, forming bundles called immune complexes ^[1].
4. Kidney Inflammation: These immune complexes travel through your bloodstream and can deposit in your kidneys’ filtering units (the glomeruli), specifically accumulating in the supporting tissue called the mesangium ^[1]. Once deposited, they can activate inflammatory pathways and cause kidney injury ^[6].

(Note: Some people who do not have IgA nephropathy also have these altered antibodies, which is why researchers know this process is only part of a complex puzzle ^[7].)

Is IgA Nephropathy Genetic?

IgA nephropathy does have a genetic link, but it is not passed down in a predictable way like eye color. Research shows that having certain genes makes your immune system more susceptible to producing the altered IgA antibodies ^[4][8].

However, having susceptibility genes does not guarantee you will get the disease. While familial clustering does happen—one study estimated that roughly 1 in 7 patients has another affected family member—the vast majority of people with IgA nephropathy are the only ones in their family to have it ^[5][9].

Should my family be tested?
Because there is no single routine predictive genetic test for typical IgA nephropathy, routine genetic screening is not universally recommended for relatives ^[10]. However, it is a good idea to discuss family screening with a doctor ^[10]. Many clinicians suggest that first-degree relatives (parents, siblings, children) have periodic, simple urine tests (urinalysis) and blood pressure checks to look for signs of kidney inflammation, such as microscopic blood or protein ^[10][11]. Keep in mind that a normal urine test does not eliminate future risk, and testing schedules should be individualized.

Persistent familial hematuria (blood in the urine) can also reflect a different genetic condition, such as COL4A3, COL4A4, or COL4A5-related disorders (including Alport syndrome), which can coexist with or look like IgA nephropathy ^[12]. If multiple relatives are affected, or if there is a history of early kidney failure or hearing/vision loss, your doctor may suggest specialized genetic testing ^[13].

Is IgA Nephropathy Contagious?

IgA nephropathy is not contagious ^[2]. You cannot catch it from someone, and you cannot give it to anyone else.

This question often comes up because many people first notice symptoms—like dark, tea-colored, or bloody urine—during or right after they have a cold, sore throat, or gastrointestinal infection ^[2][14].

• You did not “catch” the kidney disease from the cold virus.
• Instead, the infection can trigger your immune system to produce more IgA antibodies to fight the germ ^[2].
• This immune activity can sometimes trigger a “flare” of kidney inflammation, leading to visible blood in the urine ^[2][14].

When to Seek Care: While dark urine can happen during a cold, you should not assume every episode is just a routine flare. Contact your care team promptly if you notice new visible blood in your urine, or a marked decrease in how much you urinate. Seek urgent medical care for severe or rapidly worsening swelling, shortness of breath, severe headache, or markedly elevated blood pressure.

Did I Do Something to Cause This?

It is very common to search for a reason when you receive a serious diagnosis, but you did not cause your IgA nephropathy ^[1][4].

Researchers are investigating how environmental factors—such as the bacteria naturally living in your gut (the microbiome)—might influence the immune system and play a role in the disease ^[15][3]. However, these are complex biological relationships ^[15]. There is no specific food you ate, exercise routine you skipped, hygiene habit you missed, or stressful event you experienced that caused this condition ^[3][16].

No specific diet has been shown to cure or prevent IgA nephropathy ^[17]. Moving forward, your focus should be on working with your nephrologist (kidney specialist) and a renal dietitian to protect your kidney function. They will help you individualize any medication, diet, or lifestyle adjustments based on your specific kidney function, blood pressure, and protein levels ^[18][19].