IgA nephropathy overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Ali Poyan Mehr, M.D. [2] Associate Editor(s)-in-Chief: Olufunmilola Olubukola M.D.[3]
Overview
IgA nephropathy (Berger’s disease) is considered the most common primary chronic glomerulonephritis.[1] IgA nephropathy is defined immune-histologically by mesangial deposits of IgA, often accompanied by less intense staining for IgM and/or IgG and C3, in the absence of a systemic disease [2]. IgAN has been differentiated from Henoch- Schönlein purpura (HSP), which is clearly a systemic illness with vasculitis.
The clinical syndrome of IgA nephropathy is often unpredictable, although classically it is recognized as a nephritic syndrome with a presentation of recurrent painless gross hematuria following a respiratory or gastrointestinal tract infection in a young male patient. Nonetheless, asymptomatic IgA nephropathy with microscopic hematuria is not uncommon.[3] Although not frequently performed, the definitive diagnosis to confirm the clinical suspicion of IgA nephropathy is kidney biopsy that not only carries diagnostic benefit, but also has prognostic implications.
IgA nephropathy is a progressive kidney disease that often leads to End Stage Renal Disease (ESRD) due to lack of specific treatments or therapies for this disease. IgA Nephropathy is diagnosed by electron microscopy of a kidney biopsy specimen showing immunological deposits of predominantly glycosylated but non-galactosed linked IgA1 in the mesangium of the kidney glomeruli. These IgA immune complexes deposit comprises of mainly glycosylated immunoglobulin A1 (IgA) with some complement C3 and immunoglobulins G/M (IgG/ IgM).
Historical Perspective
IgA nephropathy (Berger disease) was first described by Jean Berger, a pathologist, and Nicole Hinglais, an electron microscopist, in 1968 in France.
Classification
IgA nephropathy may be classified according to its association to other pathology or by its histological features. When IgA nephropathy occurs in isolation, it is called "primary IgA nephropathy". In converse, if IgA nephropathy is a consequence of a more systemic disease, it is called "secondary IgA nephropathy". Additionally, IgA nephropathy may be histologically classified according to the oxford classification of IgA nephropathy as mesangial hypercellularity, segmental glomerulosclerosis, endocapillary hypercellularity, or tubular atrophy/interstitial fibrosis.
Pathophysiology
IgA nephropathy is characterized by the presence of aberrant IgA1 immunoglobulins deposited on the glomerular mesangium. IgG and IgM may also be present to a much lower extent. On the other hand, serum IgA1 levels are elevated in patients with IgA nephropathy in 30-50% of cases. IgA1 subtypes contain galactose-deficient 3-6 O-glycans that may act as binding sites for anti-N-acetyl-galactosamine antibodies. These antibodies have been shown to be expressed following antigenic exposure to certain infectious agents. Currently, IgA nephropathy is believed to be a 4-hit process that eventually leads to IgA deposition on glomerular mesangium. Although mesangial deposition is most commonly seen in patients with IgA nephropathy, other pathological features might still be present.
Causes
The cause of primary IgA nephropathy is unknown. Additionally, there are no known infectious or environmental associated factors. However, IgA nephropathy is associated with some genetic mutations and familial clustering as a postulated cause of primary IgAN. Liver cirrhosis, celiac disease, HIV infection are the most common etiologies associated with glomerular IgA deposits and thus secondary IgA nephropathy.
Epidemiology and Demographics
IgA nephropathy is currently the most common cause of primary glomerulonephritis globally, and it is the most common primary chronic glomerulonephritis in the developed world. IgA nephropathy comprises approximately 10% of all biopsy-proven glomerulonephritis in the USA, 20% of those in Europe and 40-50% of those in Asia. The kidney biopsies are not routinely performed for all patients with kidney diseases; hence, IgA nephropathy is perhaps under-diagnosed, and its true prevalence remains unknown.
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References
- ↑ D'Amico G (1987). "The commonest glomerulonephritis in the world: IgA nephropathy". Q J Med. 64 (245): 709–27. PMID 3329736.
- ↑ Julian BA, Waldo FB, Rifai A, Mestecky J (1988). "IgA nephropathy, the most common glomerulonephritis worldwide. A neglected disease in the United States?". Am J Med. 84 (1): 129–32. PMID 3337116.
- ↑ Donadio JV, Grande JP (2002). "IgA nephropathy". N Engl J Med. 347 (10): 738–48. doi:10.1056/NEJMra020109. PMID 12213946.