Acute infantile thrombocytosis and vitamin K deficiency associated with intracranial haemorrhage.

A 5-week-old breast-fed girl presented unconscious and convulsing with heavily blood-stained CSF under increased pressure. This was associated with oozing from venepuncture sites, a grossly prolonged prothrombin time, and a raised platelet count. The prothrombin time became normal 18 hours after she had been given parenteral vitamin K and a transfusion of fresh plasma and red cells, but the thrombocytosis persisted. A moderate communicating hydrocephalus also remained and was treated, and one year later health and development appeared normal. The thrombocytosis resolved after a few weeks and has not recurred.