Kasabach-Merritt Phenomenon in a Neonate with a Rapidly Enlarging Vascular Tumor of the Foot and Hypercalcemia: A Case Report

Abstract

Kasabach-Merritt phenomenon (KMP) is a potentially life-threatening consumptive coagulopathy characterised by severe thrombocytopenia and coagulation abnormalities associated with aggressive vascular tumours, particularly kaposiform hemangioendothelioma (KHE) and tufted angioma. We report the case of a 10-day-old term male neonate who presented with a rapidly enlarging vascular mass of the right foot. The lesion had been present since birth and had rapidly increased in size, reaching 7 cm in diameter, with a violaceous nodular surface, multiple telangiectasias, focal ulceration, and a palpable thrill. Laboratory investigations revealed profound thrombocytopenia (platelet count ~4,000/mm³), elevated D-dimer levels, hypofibrinogenemia, prolonged prothrombin time, and prolonged activated partial thromboplastin time, consistent with consumptive coagulopathy. Despite high-dose intravenous methylprednisolone, the coagulation abnormalities initially improved, but the vascular mass continued to enlarge, reaching 10 cm. Doppler ultrasonography demonstrated marked arterial and venous proliferation with peripheral arteriovenous microfistulas, while magnetic resonance imaging showed extension into the leg and deep tissues, reaching the underlying bone without bone lysis. The clinical course was additionally complicated by hypercalcaemia associated with suppressed parathyroid hormone and increased urinary calcium excretion. Because of progressive tumour enlargement despite corticosteroid therapy, vincristine was introduced at 0.05 mg/kg intravenously once weekly, resulting in rapid platelet recovery and marked regression of the vascular mass. This case highlights the severity of KMP in the neonatal period and the importance of early recognition, multidisciplinary management, and timely escalation of therapy in patients with progressive vascular tumours.