Increased serum IgD concentrations in children with Henoch-Schönlein purpura.

Serum IgD concentrations were measured in 39 children with Henoch Schonlein purpura (HSP) and 40 control children by means of radial immunodiffusion. Serum IgG, IgA and IgM concentrations in the HSP patients were measured by nephelometry. The geometric mean IgD concentration in children with HSP (16.7 microg/ml) was significantly higher than in control children (9.1 microg/ml; P=0.03). Serial testing in 10 HSP patients revealed no significant change in IgD concentrations over periods ranging from 1 to 12 months. There was no relationship between IgD and IgA concentrations in the HSP patients. Nineteen of the 39 HSP patients (49%) had nephritis. The mean IgD concentration in patients with nephritis (10.7 microg/ml) did not differ from control values, but was significantly lower than the mean IgD level in the remaining 20 patients who did not have nephritis (25.4 microg/ml; P=0.02). These results indicate that serum IgD levels are increased in children with HSP who did not have nephritis. IgD concentrations in patients with nephritis were similar to levels in control children.