Anti-glomerular basement membrane antibody (anti-GBM Ab) is an antibody which is found in Goodpasture's syndrome but not found in microscopic polyangiitis.
Some sources consider "anti-GBM disease" and "Goodpasture disease" to be synonymous terms describing histological presentation, reserving the term "Goodpasture syndrome" for clinical presentation.
References
Anti-glomerular basement membrane antibody Wikipedia(Text) CC BY-SA