Prevalence of elevated antithyroid antibodies and antinuclear antibodies in children with immune thrombocytopenic purpura.

The prevalence and significance of autoantibodies found at the time of diagnosis of childhood ITP were studied to correlate their presence with risk for development of chronic ITP. Children presenting with acute or chronic ITP to The James Whitcomb Riley Hospital for Children between July 1993 and September 1994 were tested at study entry and followed for the presence of antithyroid antibodies (ATA), antinuclear antibodies (ANA), Coombs' reactivity, and anti-human immunodeficiency virus (HIV) antibodies. Grouped data were evaluated for significance using Fisher's exact t-test. Thirty-one patients were enrolled in the study with a median age of 8 years (range 17 months-16 years) and male-to-female ratio of 1:1.8. Forty-two percent of these children had an acute course of ITP, and 58% of children had a chronic course of ITP. Of children with acute ITP, three (23%) of the patients had an acute nonplatelet autoantibody detected. Of the children with chronic ITP, six (33%) of the children had at least one abnormal antibody value. Five children (16%) tested positive for ATA: 2 children with acute ITP and 3 with chronic ITP. Five children had positive ANA, and of these children, 4 (80%) had chronic ITP. Sixty-seven percent of patients testing positive for autoantibodies were female, and 67% of all patients were 12 years of age or older. Three patients, 1 with acute ITP and 1 with chronic ITP, had insignificant abnormal thyroid function tests (these children had minimally elevated T3 with otherwise normal thyroid function, and none of these children had autoantibodies). No patients included in the study tested positive for HIV. Our results suggest that patients with acute ITP who also have other autoantibodies may be more likely to develop chronic ITP than those lacking these autoantibodies. Larger studies are needed to determine whether the presence of ATA or ANA is predictive of clinically significant autoimmune disease.