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IgA nephropathy (also known as IgA nephritis, IgAN, Berger’s disease and synpharyngitic glomerulonephritis) is a form of glomerulonephritis (inflammation of the glomeruli of the kidney). This should not be confused with Buerger’s disease, an unrelated condition.
IgA nephropathy is the most common glomerulonephritis throughout the world. Primary IgA nephropathy is characterized by deposition of the IgA antibody in the glomerulus. There are other diseases associated with glomerular IgA deposits, the most common being Henoch-Schönlein purpura, which is considered by many to be a systemic form of IgA nephropathy. Henoch-Schönlein purpura presents with a characteristic skin rash, occurs more commonly in young adults (16-35 yrs old) and is associated with a more benign prognosis than IgA nephropathy, which typically presents with hematuria in adults and may lead to chronic renal failure.
The classic presentation (in 40-50% of the cases) is episodic frank hematuria which usually starts within a day of an upper respiratory tract infection (hence synpharyngitic, as opposed to post-streptococcal glomerulonephritis which occurs some time after an initial infection). Flank pain can also occur. The frank hematuria resolves after a few days, though the microscopic hematuria persists. These episodes occur on an irregular basis, and in most patients, this eventually stops (although it can take many years). Renal function usually remains normal, though rarely, acute renal failure may occur (see below). This presentation is more common in younger adults.
A smaller proportion (20-30%), usually the older population, have microscopic hematuria and proteinuria (less than 2 grams of protein per 24 hours). These patients may not have any symptoms and are only picked up if a doctor decides to take a urine sample. Hence, the disease is picked up more commonly in situations where screening of urine is compulsory, e.g. schoolchildren in Japan.
Very rarely (5% each), the presenting history is:
A variety of systemic diseases are associated with IgA nephropathy such as liver failure, celiac disease, rheumatoid arthritis, Reiter’s disease, ankylosing spondylitis and HIV. Diagnosis of IgA Nephropathy and a search for any associated disease occasionally reveals such an underlying serious systemic disease. Occasionally, there are simultaneous symptoms of Henoch-Schönlein purpura; see below for more details on the association.
For an adult patient with isolated hematuria, tests such as ultrasound of the kidney and cystoscopy are usually done first to pinpoint the source of the bleeding. These tests would rule out kidney stones and bladder cancer, two other common urological causes of hematuria. In children and younger adults, the history and association with respiratory infection can raise the suspicion of IgA nephropathy directly. A urinalysis will show red blood cells, usually as red cell urinary casts. Proteinuria, usually less than 2 grams per day, also may be present. Other renal causes of isolated hematuria include thin basement membrane disease and Alport syndrome, the latter being a hereditary disease associated with hearing impairment. A kidney biopsy is necessary to confirm the diagnosis. The biopsy specimen shows proliferation of the mesangium, with IgA deposits on immunofluorescence and electron microscopy. However, all patients with isolated microscopic hematuria (i.e. without associated proteinuria and with normal kidney function) are not usually biopsied since this is associated with an excellent prognosis.
Other blood tests done to aid in the diagnosis include CRP or ESR, complement levels, ANA, ANCA and LDH. Protein electrophoresis and immunoglobulin levels can show increased IgA1 in 30% to 50% of all patients. may be normal or reduced. Tests such as electrolytes, renal function (creatinine, urea), total protein, serum albumin help in establishing the prognosis. Other tests such as bleeding time, full blood count, PT and PTT are done before performing a biopsy.
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