Kaposiform hemangioendothelioma (KHE) is a rare, aggressive vascular tumor frequently complicated by Kasabach–Merritt phenomenon (KMP), a life-threatening consumptive coagulopathy. Neonatal KHE-KMP management requires urgent intervention but is complicated by immunosuppression risks, especially in Bacillus Calmette–Guérin (BCG)-vaccinated infants.

A full-term male neonate with prenatal right upper limb thickening presented postnatally with a violaceous, firm mass. Laboratory findings confirmed KMP. Due to recent BCG vaccination, sirolimus was initially withheld. First-line therapies failed, prompting sirolimus initiation on day 3, supplemented by fibrinogen transfusions.

Platelets normalized by day 13 (283 × 109/L) with marked tumor regression. Transient fever/diarrhea resolved with supportive care. At discharge (day 27), platelets stabilized (183 × 109/L). Three-month follow-up showed sustained platelet recovery (268–532 × 109/L), near-complete tumor resolution, and age-appropriate development. Prophylactic trimethoprim-sulfamethoxazole prevented infections.

Sirolimus is a critical salvage therapy for refractory neonatal KHE-KMP, even in BCG-vaccinated infants. Timely initiation reverses life-threatening coagulopathy and achieves favorable outcomes, necessitating multidisciplinary monitoring to balance immunosuppression risks.

*These two authors contributed equally to this work and share the first authorship.

This work was approved by the Institutional Ethics Committee of Gannan Medical University, and written informed consent was obtained.

Received: 30 June 2025

Accepted: 19 August 2025

Article published online:
19 September 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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