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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Nephrology

Getting the Right Diagnosis: Look-Alikes and Secondary Causes

At a Glance

An IgA-positive kidney biopsy does not by itself prove primary IgA nephropathy. Doctors combine the biopsy with symptoms, blood tests, infections, and medical history to identify IgA vasculitis, infection-related inflammation, or secondary disease linked to the liver, bowel, or immune system.

When a kidney biopsy reveals IgA deposits, it is a major piece of the diagnostic puzzle—but it is not the whole picture. Having IgA in your kidneys does not automatically mean you have “primary” IgA Nephropathy (IgAN). Several other conditions can leave these same microscopic footprints, and distinguishing between them is critical because the treatments are often completely different [1][2].

The Systemic Cousin: IgA Vasculitis

IgA Vasculitis (formerly known as Henoch-Schönlein purpura or HSP) is a disease where the same altered IgA1 molecules discussed in earlier pages cause inflammation in small blood vessels throughout the body [3].

Under a microscope, the kidney damage from IgA Vasculitis can look identical to primary IgAN [4]. However, doctors look for systemic “red flags” to tell them apart:

  • Skin: A characteristic rash called palpable purpura—raised, purple-red spots that usually appear on the legs and buttocks [3].
  • Joints: Pain and swelling, most often in the knees and ankles [5].
  • Stomach: Severe abdominal pain, nausea, or even digestive tract bleeding [3].

While primary IgAN is usually confined to the kidneys, IgA Vasculitis is a “whole-body” condition that requires a broader approach to management.

The Infection Trigger: IgA-Dominant IRGN

Sometimes, the IgA in your kidneys isn’t the primary problem—it’s a secondary reaction to a battle your body is fighting against a germ. This is called IgA-dominant infection-related glomerulonephritis (IRGN) [6].

This “look-alike” is most often triggered by a Staphylococcus (Staph) infection, which might be a skin infection, a deep-seated abscess, or even a dental infection [7][8]. It is more common in older adults or people with diabetes [6].

Why the distinction matters:
If you have primary IgAN, your doctor might eventually consider immunosuppression (drugs that dampen the immune system). However, if you have IRGN, using those same drugs while you have an active infection could be dangerous [9]. In IRGN, the priority is infection control—using antibiotics to clear the germ—which often allows the kidneys to improve, though renal recovery is variable and may be incomplete [9][10].

Secondary IgA Nephropathy: The “Bystander” Effect

In some cases, another chronic health condition is associated with IgA buildup in the kidneys. This is called Secondary IgA Nephropathy. In these scenarios, the kidney is often an “innocent bystander” to a disease occurring elsewhere in the body [1].

Common conditions associated with secondary deposits include:

  • Liver Disease: Conditions like cirrhosis or chronic hepatitis can prevent the liver from clearing IgA from the blood, leading to its buildup in the kidneys [11][12].
  • Digestive Disorders: Inflammatory Bowel Disease (IBD) and Celiac disease are linked to increased IgA production in the gut, which can eventually settle in the kidney filters [13][14].
  • Autoimmune Diseases: Conditions like Lupus (SLE) or certain types of arthritis can sometimes present with IgA deposits that mimic primary IgAN [15][16].

The Path to a Primary Diagnosis

Your doctor will only label your condition as “primary” IgAN once they have evaluated these other possibilities through blood tests, physical exams, and a review of your medical history, as no single biopsy stain definitively proves primary disease [1]. Confirming that your condition is primary ensures that your care team isn’t missing an underlying infection or another systemic disease that needs its own specific treatment [17][18]. Your biopsy provides the map, but your symptoms and history provide the compass.

Common questions in this guide

Do IgA deposits on a kidney biopsy prove that I have primary IgA nephropathy?
No. IgA deposits can also occur with IgA vasculitis, infection-related kidney inflammation, or conditions such as liver, bowel, and autoimmune disease. Doctors use the biopsy together with symptoms, blood tests, physical examination, and medical history to identify the cause.
How is IgA vasculitis different from IgA nephropathy?
IgA vasculitis affects small blood vessels throughout the body, while primary IgA nephropathy is usually limited to the kidneys. A raised purple-red rash on the legs or buttocks, joint pain or swelling, and abdominal symptoms may point to IgA vasculitis, although kidney biopsy findings can look the same.
What is IgA-dominant infection-related glomerulonephritis?
It is kidney inflammation caused by an immune response to an infection, often a Staphylococcus infection of the skin, a dental infection, or an abscess. Treatment focuses first on controlling the infection with antibiotics because immunosuppressive medicines can be dangerous during an active infection. Kidney recovery varies and may be incomplete.
What health conditions can cause secondary IgA nephropathy?
Secondary IgA deposits may occur with cirrhosis or chronic hepatitis, inflammatory bowel disease, celiac disease, lupus, or some forms of arthritis. These conditions can increase IgA production, reduce its clearance, or otherwise be associated with deposits in the kidney. The care plan depends on the underlying condition.
If an infection caused my kidney inflammation, will I need immunosuppressive medicine?
Not necessarily. When active infection-related kidney inflammation is suspected, doctors generally prioritize identifying and treating the infection, often with antibiotics, before considering medicines that suppress the immune system. Your nephrologist will base this decision on the infection, biopsy, kidney function, and other test results.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my lab work, have we ruled out systemic conditions like Lupus or IgA Vasculitis that could be causing these IgA deposits?
  2. 2.Could my kidney issues be related to my history of liver disease, Inflammatory Bowel Disease, or Celiac disease?
  3. 3.Since my biopsy showed IgA deposits, did we rule out IgA Vasculitis by checking for skin, joint, or stomach symptoms?
  4. 4.If my kidney inflammation was triggered by a recent infection, do I still need immunosuppressants, or should we focus on treating the infection first?
  5. 5.Do I have any signs of 'Lupus' or other autoimmune conditions that could be causing these IgA deposits?

References

References (18)
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    IgA Nephropathy in Adults: A Review.

    Stoneman S, Teh JW, O'Shaughnessy MM

    JAMA 2026; (335(9)):799-813 doi:10.1001/jama.2025.25020.

    PMID: 41587026
  2. 2

    The Emerging Role of Complement Proteins as a Target for Therapy of IgA Nephropathy.

    Rizk DV, Maillard N, Julian BA, et al.

    Frontiers in immunology 2019; (10()):504 doi:10.3389/fimmu.2019.00504.

    PMID: 30941137
  3. 3

    IgA Vasculitis and IgA Nephropathy: Two Sides of the Same Coin?

    Pillebout E

    Seminars in nephrology 2024; (44(5)):151571 doi:10.1016/j.semnephrol.2025.151571.

    PMID: 40069065
  4. 4

    Navigating Adult-Onset IgA Vasculitis-Associated Nephritis.

    Gan MY, Chua FZY, Chang ZY, et al.

    Life (Basel, Switzerland) 2024; (14(8)) doi:10.3390/life14080930.

    PMID: 39202674
  5. 5

    Adenovirus: a possible trigger for IgA vasculitis in children.

    Mannu A, Vasudevan B, Kashif AW, Kumari L

    BMJ case reports 2025; (18(2)) doi:10.1136/bcr-2024-262856.

    PMID: 39971621
  6. 6

    Clinicopathologic features of infection-related glomerulonephritis with IgA deposits: a French Nationwide study.

    Miquelestorena-Standley E, Jaulerry C, Machet MC, et al.

    Diagnostic pathology 2020; (15(1)):62 doi:10.1186/s13000-020-00980-6.

    PMID: 32460869
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    Clinicopathologic features of IgA-dominant infection-associated glomerulonephritis: a pooled analysis of 78 cases.

    Bu R, Li Q, Duan ZY, et al.

    American journal of nephrology 2015; (41(2)):98-106 doi:10.1159/000377684.

    PMID: 25765902
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    Short-Term Outcomes of Infection-Related Glomerulonephritis in Diabetes Mellitus.

    T S A, Kaliaperumal T, Fernando E, et al.

    Cureus 2024; (16(8)):e67238 doi:10.7759/cureus.67238.

    PMID: 39301381
  9. 9

    IgA Dominant Infection Related Glomerulonephritis Mimicking Primary IgA Nephropathy in Methicillin-Sensitive Staphylococcus aureus Osteomyelitis.

    Klor B, Acharya PC, Cunningham I, et al.

    International journal of nephrology and renovascular disease 2026; (19()):578405 doi:10.2147/IJNRD.S578405.

    PMID: 42125487
  10. 10

    Successful hemodialysis withdrawal with glucocorticoid treatment after achieving infection control in a case of crescentic IgA-dominant staphylococcus-associated glomerulonephritis.

    Nishiyama Y, Matsumura M, Yasui Y, et al.

    CEN case reports 2026; (15(5)).

    PMID: 42752782
  11. 11

    A Case of Hepatic Glomerulosclerosis with Monoclonal IgA1-κ Deposits.

    Okabayashi Y, Tsuboi N, Nakaosa N, et al.

    Case reports in nephrology 2018; (2018()):4748357 doi:10.1155/2018/4748357.

    PMID: 30364076
  12. 12

    [Chronic kidney injury in patients with liver diseases - Reappraising pathophysiology and treatment options].

    Scurt FG, Bose K, Canbay A, et al.

    Zeitschrift fur Gastroenterologie 2021; (59(6)):560-579 doi:10.1055/a-1402-1502.

    PMID: 33728618
  13. 13

    IgA nephropathy and infections.

    Rollino C, Vischini G, Coppo R

    Journal of nephrology 2016; (29(4)):463-8 doi:10.1007/s40620-016-0265-x.

    PMID: 26800970
  14. 14

    Inflammatory Bowel Disease Is More Common in Patients with IgA Nephropathy and Predicts Progression of ESKD: A Swedish Population-Based Cohort Study.

    Rehnberg J, Symreng A, Ludvigsson JF, Emilsson L

    Journal of the American Society of Nephrology : JASN 2021; (32(2)):411-423 doi:10.1681/ASN.2020060848.

    PMID: 33177116
  15. 15

    Immunostaining for galactose-deficient immunoglobulin A is not specific for primary immunoglobulin A nephropathy.

    Cassol CA, Bott C, Nadasdy GM, et al.

    Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association 2020; (35(12)):2123-2129 doi:10.1093/ndt/gfz152.

    PMID: 31369128
  16. 16

    Progress in Pathogenesis of Immunoglobin A Nephropathy.

    Stanley JC, Deng H

    Cureus 2020; (12(6)):e8789 doi:10.7759/cureus.8789.

    PMID: 32724739
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    Liver Disease-Associated Glomerulopathies.

    Kanduri SR, Peleg Y, Wadhwani S

    Advances in kidney disease and health 2024; (31(2)):147-156 doi:10.1053/j.akdh.2023.11.002.

    PMID: 38649219
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    Staphylococcus Infection-Associated GN - Spectrum of IgA Staining and Prevalence of ANCA in a Single-Center Cohort.

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    Clinical journal of the American Society of Nephrology : CJASN 2017; (12(1)):39-49 doi:10.2215/CJN.05070516.

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This page is for informational purposes only and does not constitute medical advice. A nephrologist should interpret your kidney biopsy together with your symptoms, blood tests, infections, and medical history.