Immunoglobulin A (IgA) nephropathy, also known as Berger disease, is a kidney disorder characterized by the deposition of IgA in the glomeruli, leading to inflammation and potential damage. It is the most common primary glomerulonephritis worldwide. Here are five things to know about IgA nephropathy.
1. Disease-modifying therapies for IgA nephropathy have become available only recently.
The past few years have brought development of the first disease-modifying therapies to reduce proteinuria for adults with primary IgA nephropathy who are at risk for rapid disease progression. In 2021, the US Food and Drug Administration (FDA) approved a targeted-release formulation of the corticosteroid budesonide for these patients. This formulation delivers the drug to the distal ileum, targeting Peyer patches — the site of IgA production — while minimizing the adverse effects associated with systemic corticosteroid therapy.
The FDA most recently approved sparsentan, a nonimmunosuppressive therapy that combines an endothelin type A receptor antagonist with an angiotensin II type 1 receptor antagonist, for the same indication in 2023.
In addition, several studies have reported benefits with the use of sodium-glucose cotransporter 2 (SGLT2) inhibitors in the treatment of patients with IgA nephropathy at high risk for progression, although this use is still investigational.
2. The most common sign in patients with IgA nephropathy is blood in the urine.
The most common clinical manifestation of IgA nephropathy is microscopic or gross hematuria. Hematuria is often recurrent and may follow upper respiratory tract or other infections. The presence of blood in the urine may be episodic and can vary in severity.
Proteinuria is another key feature of IgA nephropathy. It may range from mild to moderate and, in some cases, can even progress to nephrotic-range proteinuria. The level of proteinuria is an important indicator of disease severity and prognosis. Persistent and significant proteinuria may be associated with an increased risk for progression to chronic kidney disease.
3. Five histologic features are widely used to predict clinical outcomes.
The Oxford classification of IgA nephropathy, or MEST score, published in 2009, comprises four histologic features that are independent predictors of clinical outcome: mesangial and endocapillary hypercellularity, segmental glomerulosclerosis, and interstitial fibrosis/tubular atrophy. In 2017, the IgA Nephropathy Classification Working Group added glomerular crescent formation to the Oxford classification, to form the MEST-C score.
If any of these features are seen, the prognosis can generally be assumed to be poor. Proteinuria, hypertension, elevated creatinine, and a decreased estimated glomerular filtration rate are some of the other factors that can contribute to poor clinical outcomes in patients with IgA nephropathy.
4. IgA nephropathy can eventually progress to end-stage kidney disease.
Progressive kidney dysfunction can occur in some individuals with IgA nephropathy. This may manifest as a gradual decline in glomerular filtration rate, leading to chronic kidney disease over time. In addition, up to 20% of patients progress to end-stage kidney disease within 10 years. The risk for renal impairment varies among individuals, and certain clinical and histologic features may influence the prognosis.
Hypertension is a common complication of IgA nephropathy. The mechanisms underlying hypertension in IgA nephropathy are complex and may involve alterations in the renin-angiotensin-aldosterone system and salt-water balance. Controlling blood pressure is important in managing IgA nephropathy to help slow the progression of kidney damage.
5. Definitive diagnosis requires a renal biopsy.
There are currently no validated diagnostic serum or urine biomarkers for IgA nephropathy, which, according to KDIGO (Kidney Disease: Improving Global Outcomes), requires a renal biopsy to make a definitive diagnosis. The characteristic finding is the deposition of IgA in the glomeruli, typically in the mesangial area. The biopsy can also provide information about the degree of inflammation, scarring, and other histologic features that help guide treatment decisions and predict outcomes.
Dr. Alper, associate professor, department of medicine, section of nephrology, Tulane University School of Medicine, New Orleans, has disclosed no relevant financial relationships.
A version of this article appeared on Medscape.com.