Membranoproliferative glomerulonephritis

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Membranoproliferative glomerulonephritis (MPGN), also known as mesangiocapillary glomerulonephritis (esp. in Europe), can be used to describe a histomorphological pattern of glomerular disease or as a disease label, with potential confusion arising when this is not made explicit (a similar problem arises with focal segmental glomerulosclerosis).

Info bulb.pngTraditional Classification
Type I
subendothelial deposits
Type II
dense deposits in glomerular basement membrane
Type III
subepithelial and subendothelial deposits

The traditional classification into types I to III, partly based on the location of immune deposits, is becoming obsolete as the underlying aetiology in specific cases are becoming better understood.[1]

The same disease can result in type I or III pattern. But, as is common in renal pathology, different diseases can cause the same pattern. For instance, both IgA nephropathy and lupus nephritis may show membranoproliferative patterns.

Type II MPGN was named as some cases showed similarity to type I, but the underlying complement defects may result in histological patterns other than MPGN[2] such that the preferred term is dense deposit disease. Where complement dysregulation is involved, further genetic and serological tests can also define the precise aetiology, e.g. within C3 glomerulopathy (which encompasses dense deposit disease), more than one component of the complement system may be abnormal.

MPGN is better thought about as primary or secondary, then divided into those with complement deposition only versus those with immune complex deposition. These factors are not made explicit in the traditional classification. Where aetiology is known, this can be used to qualify the diagnosis. Once these cases are appropriately labelled, the numbers of idiopathic MPGN is relatively small.

Several secondary causes are also known, such as hepatitis C and other bacterial, viral or fungal infections.

References

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