In utero presentation of aggressive systemic mastocytosis in a neonate.

Mastocytosis is a clinically heterogenous disease characterized by mast cell hyperplasia in skin, bone marrow and/or visceral organs. Cutaneous mastocytosis is more frequently observed in children, whereas indolent systemic mastocytosis is more commonly observed in adults. Aggressive systemic presentation, particularly of the neonate, is exceptionally rare. We present a rare case of congenital aggressive systemic mastocytosis. The patient was a 37-week-old male, born by caesarean section owing to hepatosplenomegaly and ascites diagnosed in utero, who exhibited extensive cutaneous and systemic manifestations of mastocytosis at birth. Mutation analysis of c-KIT identified D816V mutation in exon 17. Although initial bilateral bone marrow aspirates demonstrated no mast-cell infiltrates or haematological neoplasm, subsequent bone-marrow biopsies postmortem exhibited multifocal mast-cell aggregates. Clinical course was complicated by bacteraemia and cardiorespiratory failure, leading to death at 10 weeks.