Wednesday, October 18, 2017

General Information

Background

IgA nephropathy is the commonest cause of chronic glomerulonephritis, and a common cause of chronic renal failure. In many national registries it accounts for around 10% of all dialysis and transplant patients. The disease was first characterised by the Parisian histopathologist Jean Berger, shortly after the availability of immunohistological antibodies first made it possible to stain renal biopsies for the presence of immune deposits. In 1968 Berger reported that in some biopsies of patients with chronic glomerulonephritis IgA was the predominant immune globulin (although most also contained IgG). The disease is therefore sometimes referred to as Berger's disease. Since that time a good understanding of the clinical presentation, natural history and prognosis of IgA nephropathy has been achieved, some progress has been made towards understanding its pathogenesis, and a number of effective treatments have been identified in well-designed prospective randomised controlled trials.

Clinical Presentation

There are two principal forms of presentation. The more dramatic is the sudden onset of macroscopic haematuria, often accompanied by loin pain. This can occur simultaneously with a sore throat, or more rarely with other acute mucosal infections. The urine is usually coloured bright red, and the sufferer can be quite alarmed by this symptom. Although it can occur at any age, this presentation is most commonly experienced by young men. This form of the disease often has a favourable outcome. In a diagnostic sense it should be contrasted with post-infectious glomerulo-nephritis, in which macroscopic haematuria occurs 10-14 days after a sore throat, and the urine is usually dark brown (the colour of a cola drink or black tea). The more insidious but more serious clinical presentation takes place when urinary sediment abnormalities (blood and protein on dipstick) or impaired renal function (raised serum creatinine) are detected at a routine health check. This form of IgA nephropathy is more often diagnosed in middle aged adults and has a poorer prognosis. A renal biopsy is usually performed after either form of presentation. The presence of predominant IgA staining on immunohistochemistry confirms the diagnosis.

Natural History

20-30% of patients with IgA nephropathy can expect to reach end stage renal failure (requiring dialysis or a kidney transplant) within 10-20 years of first diagnosis. Another 30-50% will continue to have grumbling glomerulonephritis. In the fortunate remainder the symptoms will resolve and a favorable prognosis is enjoyed. Many retrospective case series have been published aimed at identifying risk factors for a poor prognosis. In most of these hypertension, proteinuria (>1g/day), and reduced renal function at diagnosis are identified as the clinical risk factors for a poor outcome. On renal biopsy an interstitial round cell infiltrate is the most commonly reported marker of adverse outcome.

Management

In a newly diagnosed patient with IgA nephropathy the glomerular filtration rate (GFR) should be estimated formally by clearance of a radioactive tracer or by the use of the Cockcroft-Gault formula. Regular (usually annual) estimation of GFR is the cornerstone of rational management. 24 hour urine protein should be measured directly or by the use of the protein:creatinine ratio, and blood pressure should be monitored carefully. Many clinicians see the newly diagnosed patient every three months in the first year, to gauge the rate of change of renal function; in more stable patients the interval can be extended gradually to 12 months. Three interventions have been shown in single-agent prospective randomised controlled trials to be effective in slowing the progression of renal failure in IgA nephropathy: fish oil, steroids and ACE inhibitors. There have as yet been no studies published of the use of these agents in combination. Because of the variability in prognosis, it is not appropriate to offer these treatments to all IgA nephropathy patients. The decision to commence treatment depends on the presence of markers of adverse outcome and the observed natural history, and is usually the province of the nephrologist.



Further information for health professionals can be found at the following websites. The International IgA Nephropathy Network includes these links for the interest of visitors to this site, and does not necessarily endorse all their content. Users of the Internet should use their discretion and common sense when evaluating materials they find on the web.

Vanderbilt Medical Centre
The Virtual Hospital
Outline Med
Atlas of Renal Pathology
European IgA Nephropathy Consortium

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