Kasabach-Merritt syndrome arising from a vascular fistula

A 58-year-old woman presented with gum bleeding, hematuria, and cutaneous ecchymoses. Left hip replacement had been performed five years prior. The overall findings of our work-up were consistent with ongoing DIC triggered by the presence of an arterio-venous left femoral fistula. The patient was treated successfully with fresh frozen plasma, the fistula was surgically repaired and a stent was placed. On the second day, bleeding had resolved and laboratory values reverted to normal. This uncommon scenario is reminiscent of the Kasabach-Merritt syndrome and well illustrates that patients with an arterio-venous fistula can sometimes present with atypical features. The Kasabach-Merritt syndrome is reported in pediatric and adult patients with giant hemangiomas and angiosarcomas. Adult cases are described also in association with hematomas and large vascular aneurysms. The underlying pathophysiology is the sequestration and consumption of platelets and clotting factors with uncontrolled formation of microthrombi within the vascular lesion. DIC and a microangiopathic hemolytic anemia can subsequently develop. Mechanistic pathways of the Kasabach-Merritt syndrome in the context of a vascular fistula are shared with the more common causes of the syndrome. We speculate that the endothelial dysfunction and injury caused by the flow shear were the pivotal triggers of the aberrant trapping of platelets, the consumptive coagulopathy, and the formation of microthrombi within the fistula. Mortality rate can be as high as up to 40%. The Kasabach-Merritt syndrome could represent the only clinical feature of an otherwise occult vascular fistula. Emergency physicians should be aware of this condition.