Introduction: Mesalazine or 5 aminosalicylic acid (5 ASA) is currently a first choice drug in the treatment of inflammatory bowel disease. It has been shown that it crosses the placenta and is excreted into breast milk in small quantities.
Case report: We present the case of a four month old breast fed infant, with a thrombosis of the superior sagittal sinus secondary to a severe thrombocytosis (1,124,000/mm3). The only interesting antecedent we would draw attention to, is that breast feeding had been suddenly stopped the week before. The mother, suffering Crohn s disease, had been receiving treatment with oral mesalazine throughout her pregnancy and during lactation.
Conclusions: Once other causes of the thrombocytosis had been eliminated, we based our approach on the hypothesis that it was due to prolonged intake of 5 ASA by the mother.