How to differentiate granulomatosis with polyangiitis from microscopic polyangiitis?
MPA is distinguished from GPA by the absence of granuloma formation and the presence of a necrotizing vasculitis.
Apart from that described by Dr Agarwal, MPA does not involve the upper respiratory tract. Also, most patients with MPA showed MPO ANCA pattern whereas GPA is invariably associated with PR3 ANCA pattern.
The other difference besides the one''s described by Dr Agarwal and Dr Gonzalez-Gay is in the form of lung involvement in GPA. Cavitating nodules are seen in GPA whereas DAH can occur in both.
To add to the above: MPA has a more insidious onset and progression while GPA usually presents suddenly with new symptoms evolving within days to weeks.
Definitely overlapping situations can arise especially if PR3 is positive, and sometimes the differentiation is only semantics.
Maybe it is better to classify as PR3 or MPO vasculitis as genetics, outcome, and possibly pathogenesis depends on antibody type rather than GPA/MPA phenotype.
Completely agree with dr. Ahmed and in my manuscripts I've started referring to PR3-ANCA vasculitis and MPO-ANCA vasculitis as opposed to GPA and MPA. I wrote a review about the differences between both antibodies: https://doi.org/10.1681/ASN.2014090903.
Here's the link: https://jasn.asnjournals.org/content/26/10/2314.
Hello everyone, this is a interesting review about differences and similarities between MPA anf GPA:
https://ard.bmj.com/content/72/8/1273
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