On the "easy bruising" syndrome with normal platelet count. A study of 75 patients.

Seventy-five consecutive patients with normal platelet counts were investigated for "easy bruising." All had a normal coagulation profile, and all except four were women. None were on aspirin or other antiplatelet agents. Two specific groups could be delineated. In type I (44 patients, mean age, 35), platelet function was normal to supranormal. Megathrombocyte number was elevated in 60% of patients and correlated with the presence of antiplatelet antibody in 30% of patients. In type II (31 patients, mean age, 34), platelet function was abnormal: impaired epinephrine aggregation (primary and secondary wave) in 97%, impaired connective tissue aggregation in 77%, and impaired ADP aggregation in 42%. Megathrombocyte number was elevated in 71%, and antiplatelet antibody was present in 38% of patients. The "easy bruising" syndrome can be differentiated into two categories: type I, in which a platelet abnormality is unlikely, and type II, in which a platelet abnormality exists. Elevated incidence of antiplatelet antibody in both groups suggests a possible autoimmune cause.