Cryoglobulinaemia in Henoch-Schönlein purpura.

Sera from patients with Henoch-Schönlein purpura were examined for cryoglobulinaemia. Thirty patients had acute Henoch-Schönlein purpura, with or without renal diseas; 14 had chronic nephritis after a previous episode of purpura; and 17 were well, without urinary abnormalities, after recovering from Henoch-Schönlen purpura. Raised concentrations of cryoglobulins were present in 14 (47%) of those with acute purpura, nine (64%) of those with chronic nephritis, but none of those who had recovered completely from Henoch-Schönlein purpura. This suggests that acute Henoch-Schönlein purpura and the chronic nephritis that sometimes follows it have an immune-complex pathogenesis. IgA and properdin were found in several cryoglobulins, which suggested that complement had been activated via the alternative pathway, but isolated cryoglobulins capable of splitting C3 in vitro did so via the classical pathway.