Background: Kaposiform hemangioendothelioma (KHE) is a rare, locally aggressive vascular tumor that usually presents in infancy and early childhood. It is histologically characterized by spindle-shaped endothelial cells and capillary hemangioma-like lymphatic vessels. It is frequently associated with Kasabach-Merritt phenomenon (KMP), a consumptive coagulopathy seen in over 70% of patients.

Case presentation: We describe an 11-year-old boy who presented with an atypical clinical manifestation of KHE, occurring outside the usual age group and anatomical regions with features and investigations leading to an overlapping diagnosis of enthesitis and chronic recurrent multifocal osteomyelitis, which posed a challenge in diagnosis and management. Despite treatment efforts, the symptoms persisted, eventually prompting a biopsy that confirmed KHE. 

Discussion: This case outlines the importance of considering KHE when encountering vascular tumors, particularly when presenting in uncommon sites, and without the typical features in older age groups. It also emphasizes the standing that biopsy holds in early diagnosis, management and prevention of complications.

Conclusion: A high index of suspicion for KHE should be maintained by clinicians when encountering atypical vascular or bone lesions beyond infancy and early childhood, with a consideration for biopsy when early interventions fail.

Dr. Zeenia Merali is a pediatric Junior Clinical Fellow working at the Royal National Orthopedic Hospital, Stanmore, UK. She completed her medical degree at the University of Nairobi, after which she worked in pediatrics for 2 years before relocating to the UK. She has a special interest in pediatric hematology and rare vascular disorders, and has contributed to this field through several quality improvement projects. Her current work focuses on improving early recognition for children with rare vascular tumors.