Clinical correlates in patients with elevated platelet-associated immunoglobulins.

Studies are reported pertaining to platelet-associated IgG (PAIgG) and IgM (PAIgM) in patients with thrombocytopenias considered possibly immune-mediated on clinical grounds. Approximately 14 percent of all patients with these disorders had elevated PAIgM but normal levels of PAIgG. Of patients with classic autoimmune thrombocytopenia (ITP), there was a trend toward more frequently normal levels of PAIgG in chronic ITP compared with patients with acute ITP, but this was not statistically significant. Patients with acute ITP had higher levels of PAIgG and PAIgM in general than those with chronic ITP. Patterns of PAIgG and/or PAIgM elevation were not significantly different when chronic and acute ITP were compared, nor when childhood ITP was compared with adult ITP. Patients with immune thrombocytopenias owing to malignant disorders were likely to have lower levels of PAIgG compared with those with classic ITP. Treated patients with immune thrombocytopenias showed a trend toward earlier response to therapy if they had only elevated PAIgG as opposed to elevated PAIgM alone or elevated PAIgM and PAIgG (p = 0.17). There appear to be great overlaps in the patterns and quantities of PAIgG and PAIgM in patients with immune-mediated thrombocytopenias in widely varied clinical settings. This suggests some underlying common pathophysiologic mechanisms for thrombocytopenia in these clinically diverse disorders. It is believed that the data are most consistent with the hypothesis that thrombocytopenia in patients with elevated PAIgG and/or PAIgM is most probably of immune origin even in such diverse disorders as systemic lupus erythematosus, cirrhosis of the liver, lymphoma, leukemia, cancer, or septic conditions, as well as in ITP.