Restricted Range of Motion and a Cold Upper Extremity in a Two-Year-Old Boy: Kaposiform Hemangioendothelioma of the Bone and the Brachial Plexus: A Case Report.

CASE: We report a case of kaposiform hemangioendothelioma (KHE) of the scapula in a 2-year-old boy with motor and sensory abnormalities of the left upper extremity, suggesting brachial plexus involvement. The locally invasive nature prevented resection; sirolimus therapy resulted in improvement of the motor and sensory impairment, as well as decreased tumor size on imaging. CONCLUSION: Osseous infiltration of KHE is known to occur, but its primary presentation in bone without skin involvement is rare and diagnostically challenging. Awareness of rare presentations of KHE, along with accurate histopathologic interpretation, is important to achieve a diagnosis and to differentiate KHE from more common vascular lesions (e.g., infantile hemangioma). Sirolimus therapy is emerging as a promising treatment for unresectable KHE.