Abnormalities in IgA and IgM are associated with treatment-resistant ITP

We hypothesized that immune dysregulation, as represented by abnormal immunoglobulin (Ig) levels, may increase immune thrombocytopenia (ITP) severity. A cross-sectional analysis was performed encompassing patients with ITP seen at the New York Presbyterian Platelet Disorder Center in the past 10 years. The subjects' Ig levels were measured, and subjects were analyzed for differences in treatment response. Subjects with an IgA level greater than median had a significantly increased chance of failing to respond to standard treatment (steroids, intravenous Ig, and intravenous anti-D) than did subjects with an IgA level lower than median (37 of 271, 14%; vs 22 of 281, 8%; P = .03) and an increased risk for bleeding (36 of 378, 10%; vs 19 of 386, 5%; P = .02). Subjects with an IgM less than 56 (lower limit of normal) failed to respond to standard treatment more often than patients with a normal IgM (12 of 67, 18%; vs 44 of 467, 9%; P = .05) with a trend toward worsened response to splenectomy (3 of 18, 17%; vs 36 of 86, 42%; P = .06). These observations suggest that immune dysregulation, as represented by elevations in IgA or decreased levels of IgM, are associated with ITP that is more resistant to treatment.