Sirolimus used for treatment of retroperitoneal arteriovenous malformation in a premature neonate.

We describe a case of a premature infant with antenatally detected retroperitoneal arteriovenous malformation (AVM) with extensive intraspinal extension. Treatment of the malformation with embolectomy and sclerotherapy was not feasible in view of intraspinal extensions and small size of vessels of the lesion. During a trial of propranolol over 20 days, the lesion progressed in size, roughly doubling in volume and was accompanied with deranged coagulation parameters. Treatment was therefore switched to oral prednisolone and sirolimus. The steroid was stopped after 6 weeks and sirolimus was continued with serum drug level monitoring and serial imaging of the malformation. After 4 months of sirolimus, the AVM remained at the same size as at the start of treatment, thus we propose that the drug may have arrested the growth of the lesion. This case highlights the use of sirolimus in management of AVMs in infants.