Understanding IgA nephropathy progression
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IgA nephropathy (IgAN), also known as Berger’s disease, is a chronic, progressive autoimmune kidney condition marked by deposits of abnormal immunoglobulin A (IgA) protein in the kidneys’ filtration units, called glomeruli. IgAN is one of the most common diseases affecting the glomeruli and is a leading cause of chronic kidney disease (CKD) and kidney failure worldwide, although it is less common in the general population than conditions such as diabetic kidney disease. In the U.S., diabetes is the most common cause of kidney disease, followed by high blood pressure.
Understanding the stages of CKD in IgAN progression can be helpful as you talk with your doctor about treatment options and prepare for the future.
Does IgA nephropathy have formal stages?
Severity of IgAN is defined by a combination of changes in kidney function, proteinuria (protein in the urine), and changes in kidney tissue. There are five stages of CKD, which are an important part of determining a prognosis. However, doctors usually don’t use formal stages when they talk about IgAN severity. They may, however, discuss a patient’s MEST-C score, a score based on the condition of the kidney tissue that helps doctors determine the risk level for progression, possibly in combination with the CKD stage.
How CKD staging applies to IgA nephropathy
If IgAN has affected kidney function, a doctor may diagnose CKD, which is formally staged based on two factors:
- Estimated glomerular filtration rate (eGFR): A measure of how well the kidneys clear waste from the blood and regulate electrolytes. CKD is divided into five stages based on eGFR.
- Albuminuria: The amount of albumin (a common protein) excreted in the urine, measured by the albumin-to-creatinine ratio. Albuminuria is divided into three stages.
IgAN is one of the leading causes of diseases of the kidney filters, even though it doesn’t always progress to the point of affecting kidney function. Doctors may use CKD stage as a component for assessing and monitoring IgAN progression over time.
eGFR categories G1 to G5
eGFR stages are used to classify the degree of kidney function of people with CKD. There are several stages, which are defined as follows:
- G1: eGFR ≥90, normal or high
- G2: eGFR 60-89, mildly decreased
- G3a: eGFR 45-59, mildly to moderately decreased
- G3b: eGFR 30-44, moderately to severely decreased
- G4: eGFR 15-29, severely decreased
- G5: eGFR < 15, kidney failure
CKD is formally defined as an eGFR <60 that persists for three months or more. However, a person may be considered to have CKD even if their eGFR is still in stage G1 or G2 if they have proteinuria, hematuria (blood in the urine), or other evidence of damage to the kidneys.
Albuminuria categories A1 to A3
The other component of describing the CKD stage is albuminuria. The severity of albuminuria is categorized as follows:
- A1: <30 mg/g or <3mg/mmol, normal or mildly increased
- A2: 30 mg to 300 mg/g or 3 mg to 30 mg/mmol, moderately increased
- A3: > 300 mg/g or > 30 mg/mmol, severely increased
Together with eGFR, a person’s albuminuria category helps describe how severely the kidneys have been affected. Experts use both scores to determine the overall risk to the kidneys.
Early IgA nephropathy
Early-stage IgAN may not cause enough damage to the kidneys to affect eGFR or kidney function. However, a doctor may consider a person to have stage 1 or 2 CKD (depending on their eGFR) due to IgAN, especially if they have proteinuria and visible changes to the kidneys on a biopsy. They may recommend treatment, such as dietary or lifestyle modifications or blood pressure modification, to try to prevent or slow the progression of IgAN.
Moderate loss of kidney function
Over time, IgAN can cause progressive loss of kidney function. A person may be considered to have moderate loss of kidney function once their eGFR drops to stage G3a or G3b (considered CKD stage 3), or if their eGFR is still at stage G1 or G2 but they have substantial albuminuria. At this point, a doctor may recommend more aggressive treatment options.
Advanced kidney disease and kidney failure
Sometimes, IgAN can progress into advanced CKD or kidney failure, although the estimates for how common this is vary widely. Stage 4 CKD, or stage 3 CKD with significant albuminuria, may be considered advanced kidney disease, while kidney failure is defined as stage 5 CKD, also known as end-stage kidney disease. If IgAN progresses to advanced or end-stage kidney disease, more intensive kidney support, such as dialysis or a kidney transplant, may be required.
Can someone move between stages?
IgAN is a progressive condition, so a person may move between stages over time. However, IgAN can be very variable. Some people never progress past early-stage disease, while others reach kidney failure. Seeing a doctor regularly for kidney function monitoring can help catch progression early.
What stage means for treatment and planning
Many people are diagnosed with IgAN when their CKD is already moderate or advanced. The CKD stage at diagnosis, along with the MEST-C score, may influence the treatments and monitoring strategies that a doctor recommends. Consider talking to your doctor if you have questions about your disease stage and what to expect.
IgA Nephropathy News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
