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Renal biopsy specimen, case 2. Mesangial deposits of IgA largely confined to the mesangial regions with some segmental variation (FITC-labelled anti-IgA.x 300.) CommentTumours may give rise to circulating immune complexes, and tumour-specific antibodies and antigens have been found in these complexes.2-4It has been suggested that Henoch-Schonlein purpura is mediated by immune complexes containing IgA,5 and the condition may have occurred in our patients as a result of a carcinoma, which, acting as a source of new antigens arising at an endothelial surface, provoked an IgA response.That the renal lesion in case 2 resolved on resection of the tumour would support this assumption, and there is no evidence of another source of antigen in either case.That only one episode of purpura occurred in each case may be due to factors-in host or tumour which resulted in only a transient IgA response of suitable quality or quantity for soluble immune complex formation.
Dalton et al. (Sat,) studied this question.