• Purpura;
  • thrombocytopenia;
  • childhood;
  • haemorrhage;
  • epidemiology


Aim: To describe the epidemiology of idiopathic thrombocytopenic purpura (ITP) in the Nordic countries, to define clinical subgroups and to investigate factors predicting chronic disease. Methods: A prospective registration was done from 1998 to 2000, including all children with newly diagnosed ITP aged 0–14 y and at least one platelet count <30×109/l. Results: 506 children were registered and 423 followed for 6 mo. The incidence was 4.8/105 per year. Most children were aged 0–7 y (78%), with a predominance of boys, while patients aged 8–14 y had equal representation of the two sexes. There were seasonal variations determined by variations in postinfectious cases with sudden onset. The platelet count was <10×109/l in 58%, but bleeding manifestations were mild or moderate in 97%. The insidious form (symptoms for more than 2 wk) was more frequent in older children and girls, showed little seasonal variation, had milder manifestations and ran a chronic course in more than half the cases. Intracranial haemorrhages did not occur in the first 6 mo after diagnosis. Chronic ITP developed in 25%. The strongest predictor of chronic disease was insidious onset of symptoms (OR 5.97).

Conclusion: In the Nordic countries, ITP mainly affects children aged 0–7 y, with a winter bulk of postinfectious cases superimposed on a steady occurrence of non-infectious cases. Clinically, it may be useful to distinguish between children with sudden versus insidious onset of symptoms rather than between different age groups.