Platelet-associated immunoglobulin G in childhood idiopathic thrombocytopenic purpura.

Childhood ITP is an acquired hemorrhagic disorder with a heterogeneous clinical course. We measured PAIgG levels in 20 children with ITP (7 acute, 13 chronic). Both groups had significantly greater PAIgG values than age-matched normal subjects and thrombocytopenic controls (P less than 0.001). In addition, PAIgG values in chronic ITP were significantly lower than those in acute ITP (P less than 0.003). Serial PAIgG values were obtained in some patients; most returned to normal in association with clinical recovery. The measurement of PAIgG is useful in the diagnosis and follow-up of childhood ITP. PAIgG values may assist in differentiating acute and chronic disease in children.

In vitro production of platelet-binding IgG in childhood idiopathic thrombocytopenic purpura.

We studied two boys, 9 and 10 years old, respectively, who underwent splenectomy eight months and six weeks after initially presenting as "typical" cases of childhood ITP. Splenic leukocytes from each child were cultured and net synthesis rates of IgG determined. Splenic synthesis rates of IgG were five-and sevenfold greater, respectively, than in spleens of control subjects. A significant portion of the splenic culture-produced IgG from each patient demonstrated specificity for homologous and autologous platelets. Synthesis rates of IgG were determined on serial cultures of bone marrow cells from the 10-year-old boy who failed to respond to splenectomy. His initial marrow synthesis rate of IgG was five times greater than mean control values. His synthesis rate of IgG in marrow decreased to the control range in association with immunosuppressive therapy and intesive platelet transfusions. These data suggest that (1) the spleen was a production site of platelet-binding IgG in the two children, and (2) the bone marrow may have been an additional site of production in our second patient.

The micromeasurement of free erythrocyte protoporphyrin as a means of differentiating alpha thalassemia trait from iron deficiency anemia.

Free erythrocyte protoporphyrin levels were measured in 29 individuals with alpha thalassemia trait, 19 with proved iron deficiency anemia, and 25 normal control subjects. Individuals with alpha thalassemia trait and normal iron studies had FEP levels in the normal range despite marked degrees of microcytosis. In contrast, individuals with iron deficiency anemia had marked elevation of FEP levels with similar degrees of microcytosis. Measurement of FEP levels appears to be a useful tool in differentiating alpha thalassemia trait from iron deficiency anemia.