Summary The Nordic idiopathic thrombocytopenic purpura study data showed that morbidity occurred mainly in children with thrombocytopenia lasting >3 months, whereas, the risk period with platelet counts <20 × 109/l was short and the number of bleeding events low in children with shorter disease duration. These brief, uneventful courses were predicted by developing a scoring system based on six clinical features: abrupt onset (weight 5), age <10 years (3), preceding infection (2), platelet count <5 × 109/l, wet purpura (1) and male gender (1). The score was derived and validated in two different cohorts of children. High scores (10–14) clearly identified low‐risk patients. The score provides valid prognostic information and may be useful in clinical decision‐making.

In a Nordic cohort of children with chronic ITP, one half had recovered 5 years after diagnosis, more than half never required hospitalization and <10% experienced serious bleeding episodes, always with a platelet count <20 × 10(9) /L. Aggressive management can be restricted to the minority of children with continuing severe thrombocytopenia and frequent, clinically significant bleeding events.

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Active treatment policies accelerated platelet recovery in children with short-lasting ITP but did not avert the development of chronic ITP and did not cause a reduction in morbidity during follow-up.