Idiopathic thrombocytopenic purpura in children; detection of platelet autoantibodies by immunofluorescence

There are 3 varieties of idiopathic thrombocytopenic purpura (ITP) in children: the acute, the chronic and the recurrent forms. We have tested the platelets from 80 children with these forms of ITP by an immunofluorescence test. Platelet-bound immunoglobulins were detected in 19/22 acute, 41/48 chronic and 5/10 recurrent cases of ITP, i.e. in 65 of a total of 80 cases. A significance differences between acute and chronic ITP was found in the observation that only IgM was bound to the platelets of 7/16 patients with acute ITP. In all cases of chronic ITP with a positive direct immunofluorescence test, IgG was present on the platelet membrane. It is assumed because some patients with chronic ITP do not have elavated platelet-bound immunoglobulins, and show refractoriness to immunosuppressive therapy, that in these patients the disorder is not of a humoral autoimmune nature.