Kaposiform hemangioendothelioma: clinical features, complications and risk factors for Kasabach-Merritt phenomenon Yi Ji1, Kaiying Yang1, Suhua Peng1, Siyuan Chen2, Bo Xiang1, Zhicheng Xu1, Yanan Li1, Qi Wang1, Chuang Wang1, Chuncao Xia3, Li Li4, Xingtao Liu5, Guoyan Lu6, Gang Yang1, 7, Hao Wu8 1Division of Oncology, Department of Pediatric Surgery, West China Hospital of Sichuan University, Chengdu, China 2Pediatric Intensive Care Unit, Department of Critical Care Medicine, West China Hospital of Sichuan University, Chengdu, China 3Department of Radiology, West China Hospital of Sichuan University, Chengdu, China 4Laboratory of Pathology, West China Hospital of Sichuan University, Chengdu, China 5Department of Vascular & Interventional Radiology, Chengdu Women and Children’s Central Hospital, Chengdu, China 6Pediatric Intensive Care Unit, West China Second University Hospital, Sichuan University, Chengdu, China 7Department of Pediatric Surgery, Chengdu Shangjin Nanhu Hospital, Chengdu, China 8Vascular Biology Program and Department of Surgery, Boston Children’s Hospital, Harvard Medical School, Boston, USA British Journal of Dermatology. DOI: 10.111/bjd.16601

Introduction What’s already known? Kaposiform hemangioendothelioma (KHE) is a rare vascular neoplasm that typically arises during infancy or early childhood. KHE has notably high mortality and morbidity rates due to severe associated complications. KHE patients may develop a life-threatening thrombocytopenia and consumptive coagulopathy, known as Kasabach-Merritt phenomenon (KMP).

Methods We conducted a cohort study of 146 patients diagnosed with KHE. Based on the depth of tissue/organ involvement, lesions were classified into 3 groups: superficial, mixed and deep. Major complications, which were observed before or at the time of diagnosis, were defined as events that were life threatening or could result in long-term morbidity.

Results KHE precursors or lesions were present at birth in 52.1% of patients. In 91.8% of patients, lesions developed within the first year of life. The median age at diagnosis of KHE was 2.3 months. The extremities were the dominant location, representing 50.7% of all KHEs.

Results Fig. 1 KHEs can be classified based on the depth of the lesions. Superficial lesion: a & b Mixed lesion: c & d Deep lesion: e & f

Results KMP occurred in 102 patients (69.9%). The median platelet count was 21×109/L (IQR, 9-37×109/L) at the initial presentation of KMP. In total, 49 of 102 patients (48.0%) had no evidence of KMP at the initial assessment of the lesions, but KMP developed later. Approximately 70% of patients showed KMP. A KHE diagnosis was delayed by ≥1 month in 65.7% of KMP patients.

Results Events With KMP Without KMP P-values n=102 n=44 Table 2: Major complications in KHE patients with or without KMP (n = 146) Events With KMP Without KMP P-values n=102 n=44 Thrombocytopenia 102 N/A Severe acquired hypofibrinogenemia 53 Compression of vital structures 22 4 0.098‡ Severe anemia 20 Bone-joint invasion 7 12 0.001† Decreased range of motion 13 <0.001‡ Severe pain 1 9 Pericardial effusion 6 Active organ bleeding Acute heart failure 3 Pleural effusion 2 Total 224 38 0.023#

Results Fig. 2 A rapidly enlarging KHE that involves the anterior chest wall.

Results Young age (<6 months), trunk location, large lesion size (>5.0 cm), and mixed lesion type were associated with KMP in a univariate analysis. In the multivariate analysis, only age (95% confidence interval [CI], 4.066- 34.753; P<0.001), a large lesion size (95% CI, 2.239-11.535; P<0.001) and mixed lesion type (95% CI, 1.228-7.132; P=0.016) were associated with KMP.

Discussion What does this study add? We demonstrate that KMP is common in KHE patients and contributes to various life-threatening complications, which can develop early in the disease course. Significant predictors of KMP include young age, a large lesion size and mixed-type lesion. Recognition of the clinical characteristics of KHE and the factors that predict KMP will enable clinical decision making.

Conclusions Most KHEs appeared before 12 months of age. KHEs are associated with various major complications, which can occur in combinations and develop early in the disease process. Young age, a large lesion size and mixed lesion type are important predictors of KMP.

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