Discussion
KHE is a rare vascular neoplasm during infancy and should be carefully differentiated from infantile hemangioma1. The prevalence of KHE in Massachusetts is about 1 in 100,000 children2. It can present as a raised subcutaneous mass, involving the extremities, trunk, or cervicofacial region. In addition, it may present as intrathoracic or retroperitoneal lesions in 10% of patients, not involving the skin2. The major pathological manifestations of KHE are abnormal angiogenesis and lymphangiogenesis3. Diagnosis is based on the combination of clinical, histologic, and imaging features. MRI can illustrate an ill-defined mass, hypointense or isointense compared with muscle in T1-weighted sequences, and hyperintense in T2-weighted sequences4. Although KHE is a benign vascular tumor that does not spread to other parts of the body, it can grow aggressively and is often associated with the most serious complication, KMP, which is a life-threatening complication of KHE. The KMP was first described in 1940 with characteristics of active consumptive coagulopathy5. Therefore, laboratory data can show profound thrombocytopenia and hypofibrinogenemia with elevated markers of coagulation activation. In a large cohort study2, the risk factors for KMP included the tumor location (intrathoracic or retroperitoneal involvement), the tumor depth (infiltration into muscle or fascia), and the tumor size (maximum diameter greater than 8 cm). Immediate management is needed to avoid high mortality and morbidity. It is currently thought that KMP occur in approximately 70% of KHE, but not in infantile hemangioma4,6. Given the high mortality range from 8 to 24%4,7, accurate diagnosis and prompt treatment are important. However, there is no standard treatment guideline due to the rarity of KHE.
The treatment method for KHE is mainly based on the opinions of experts, and a small number of case reports and case series. Supportive treatment should be provided first to prevent the patient’s condition from getting worse, followed by curative therapy for the underlying vascular tumor. Fresh frozen plasma or cryoprecipitate is used to correct coagulopathy. Platelets are reserved for active bleeding or before surgery, because it will exacerbate mass bleeding and platelet trapping in the tumor3,8. Although surgical resection is considered to be the standard method for the treatment of vascular tumors, it is difficult to perform during the active phase of KMP due to acute bleeding and severe coagulopathy. Since most KHE is infiltrative and may invade adjacent organs, it is almost impossible to obtain a clear tumor margin for surgery9. Arterial embolization may be an effective treatment method for KHE combined with KMP, but its main limitation is the technical difficulty of accessing the very small feeding arteries in neonates and young infants3. Previous studies have found that arterial embolization only had a temporary therapeutic effect for some cases of KMP7. According to the 2013 consensus of medical treatment for complicated KHE9, intravenous vincristine 0.05 mg/kg once a week and oral prednisolone 2 mg/kg/day or intravenous methylprednisolone 1.6 mg/kg/day are recommended as the first-line treatment for KHE patients with KMP, and oral prednisolone 2 mg/kg/day is recommended for those without KMP. Sirolimus has recently been suggested as an alternative therapy for KHE 3,8. Cashell J, et al. reported the life-saving treatment of an infant with KHE and KMP after three weeks of treatment with prednisolone, vincristine, and sirolimus10.
In the acute stage of KMP, it is difficult to perform surgery when there is evidence of bleeding tendency. On the other hand, drugs take too long to correct coagulopathy with active bleeding. Transcatheter arterial embolization may be an alternative therapy. However, to the best of our knowledge, there are no case reports of such small infants receiving arterial embolization to treat KHE. In the present case, a 9-day-old newborn underwent arterial embolization for KHE with KMP, combined with sirolimus treatment, and the outcome was favorable. Our successful experience of treating KHE with KMP revealed that transcatheter arterial embolization is feasible and can be used as an alternative to surgical resection, even in small babies.