Incidence of selective IgG2 deficiency in patients with vasculitis.

IgG2 deficiency has been recently associated with the appearance of vasculitis. None of the 42 patients with IgG2 deficiency whom we studied has a history of vasculitis. We have also studied 56 patients with vasculitis, and found four of them with IgG2 levels below the normal range for their age. As a group, the vasculitis patients did not differ in the incidence of low IgG2 levels from a normal population. Three of the four vasculitis patients with low IgG2 levels had a Henoch-Schonlein syndrome, and the association between both features was statistically significant.