Kaposiform hemangioendothelioma: A case report of a diagnostic challenge of a kaposiform hemangioendothelioma of the proximal tibia with an atypical presentation

Kaposiform hemangioendothelioma (KHE) is a rare, benign but locally aggressive vascular tumor primarily diagnosed in infancy and early childhood. It often presents with Kasabach-Merritt phenomenon (KMP), a life-threatening coagulopathy. However, atypical presentations, especially involving deep tissues or bone without skin manifestations, are rarely documented. We report the case of an 11-year-old Nigerian boy with a painful, progressively enlarging swelling over the proximal tibia, initially misdiagnosed as chronic osteomyelitis. Imaging and histopathological evaluation, including immunohistochemistry, confirmed KHE with no evidence of KMP. MRI findings revealed involvement of the gastrocnemius muscle and proximal tibia. The patient was managed successfully with intravenous vincristine and oral prednisolone, resulting in significant clinical improvement within weeks. This case emphasizes the diagnostic challenges posed by atypical KHE presentations, especially in resource-limited settings, and the critical role of early suspicion, thorough histopathology, and prompt treatment in improving outcomes.