INFANTS WITH KASABACH-MERRITT-SYNDROME DO NOT HAVE TRUE HEMANGIOMAS

Objective: In 1940 Kasabach and Merritt described an infant with a vas cular anomaly, extensive purpura, and thrombocytopenia; they called hi s lesion ''capillary hemangioma.'' Hemangioma is a benign tumor that g rows in infancy and is characterized by proliferation of endothelial c ells and regression during childhood, Although Kasabach-Merritt syndro me (KMS) is frequently mentioned as a possible complication of hemangi oma, our experience suggests that the anatomic vascular lesion underly ing the thrombocytopenia is not a ''true,'' classic, involuting type o f hemangioma of infancy and childhood. Study design: We reviewed the c linical and hemostasis data and the response to treatment in 22 cases of KMS, and we analyzed the biopsy specimens of 15 of them, Results: C linically none of the 22 patients had classic hemangioma. There was no female preponderance. All patients had severe thrombocytopenia (lowes t platelet count = 3000/mm(3)) and consumption of fibrinogen. Histolog ically, none had the typical ''capillary,'' involuting type of hemangi oma of infancy: they exhibited either a tufted angioma or a kaposiform hemangioendothelioma pattern; all specimens also contained numerous a bnormal lymphatic-like vessels; lymphatic malformation was the major c omponent in two patients, The infants exhibited a heterogeneous respon se to a number of therapeutic regimens, as noted in other reports. Sev ere morbidity was present; three of our patients died, and one had leg amputation. ''Residua'' were, in fact, residual vascular neoplasia, v ariable in duration, and not a stable fibrofatty residuum, as in class ic involuted hemangioma; only the hematologic phenomenon was ''cured'' after a period of years, Conclusions: KMS is a distinctive disease of infancy, but the underlying vascular lesion is not a ''true,'' classi c, involuting type of hemangioma of infancy, This is a different vascu lar tumor with a resemblance pathologically to either tufted angioma o r kaposiform hemangioendothelioma in association with lymphatic-like v essels, Whether the underlying lesion in KMS is a single anatomic enti ty or heterogeneous cannot be definitely concluded from this study, We need a better understanding of the pathogenesis of KMS to improve our therapeutic management.