IgA nephropathy (IgAN), also known as Berger’s disease, is the leading cause of primary glomerulonephritis all over the world. It is autoimmune in origin, characterized by the stimulation of genetically determined formation of concentration of IgA1 with galactose-deficient O-glycans in the hinge-region (Hit 1) in the blood. These stimulate anti-glycan antibody production, followed by binding with the aberrantly glycated IgA1.
The antibody-IgA1 complexes are deposited in the renal mesangial tissue. This leads to mesangial cell activation and the process is also modulated by genetic factors, determining the clinical manifestations.
IgA nephropathy may present in any of several different ways, most commonly with hematuria in the absence of any other symptoms and, to a varying extent, proteinuria. However, it can also present as rapidly progressive glomerulonephritis.
Gross hematuria recurring at intervals is the most frequent symptom and usually follows an upper respiratory infection, though other infections may also precipitate it less commonly. However, microscopic hematuria, in the absence of any other symptom, picked up on routine urine analysis, is also a major presentation.
The basic defect in IgA nephropathy is not renal but systemic. In other words, the mesangial deposition of IgA-glycan complexes is related to a higher-than-normal level of abnormally glycosylated IgA1. This stimulates mesangial cell proliferation, expansion of the mesangial matrix, with the secretion of chemicals which finally result in glomerulosclerosis and interstitial fibrous tissue deposition. There are five gene markers of increased susceptibility to IgAN, such as on:
- chromosome 6p21
- chromosome 1q32 (H locus)
- chromosome 22q22 (gene cluster)
There are several risk factors for IgA nephropathy, include white or Asian origin, Family history of IgAN or of Henoch-Schonlein purpura and males between teenage to the late thirties.
Diagnosis and treatment
IgAN is diagnosed by the clinical history followed by blood tests for renal function assessment and urinalysis, with urine immunoelectrophoresis at a later stage. A renal biopsy will confirm the diagnosis.
There is no definitive treatment to achieve cure in IgAN. Supportive treatment depends on the stage of disease and is focused on alleviation of symptoms and delaying renal failure. Thus simple hematuria and proteinuria are carefully monitored. On the other hand, once the proteinuria enters the nephrotic range, renal biopsy findings will determine the treatment. The best practice in IgAN includes angiotensin blockers, and/or corticosteroids, in patients with proteinuria > 0.5 g/24 hours and hypertension (>140/90 mm Hg). Once acute renal failure presents, it should be distinguished from acute tubular necrosis. Salt and water restriction may be advised in case of significant edema.
1-2% of IgAN patients enter end-stage renal disease (ESRD) each year dating from the time when the disease is diagnosed. Risk factors for chronic kidney disease which may progress to ESRD include hypertension, the sustained excretion of more than 1 g of protein per day, a low glomerular filtration rate or other markers of renal impairment, and the nephrotic syndrome. These patients are put on antihypertensives, to control the blood pressure while blocking the renin-angiotensin axis, using angiotensinogen-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB).
While high-dose short-term corticosteroid therapy was associated with renoprotective effects, in contrast to low-dose long-term steroids, steroid therapy was linked to a 55% increased risk for adverse events as well overall.
IgA nephropathy may progress to chronic renal insufficiency. 25-30 percent of patients enter end-stage renal disease within two decades. There are several clinical and histopathologic predictors of this progression. IgAN frequently recurs after a renal transplant because of the genetic susceptibility to the disease, and approximately 10% of grafted kidneys are lost to such recurrences.