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Kasabach-Merritt syndrome (KMS) is characterised by the association of a vascular tumour with severe thrombopaenia and various degrees of consumption coagulopathy (most commonly marked by decreased levels of fibrinogen, presence of elevated levels of soluble complexes, and very high levels of D-dimers). The prevalence is unknown but the syndrome is very rare. Onset is rapid with formation of an ecchymotic and inflammatory mass. The vascular tumours associated with KMS are either congenital or acquired (usually before 6 months of age). KMS, as described in 1940, is by definition a syndrome affecting infants. In the anatomical substratum, the associated vascular tumours appear to be quite typical. The tumours were long considered as an infantile haemangioma. However, none of the clinical features, residual lesions and histological characteristics of the tumour resemble those of a haemangioma. It is now established that the tumour associated with KMS is either a tufted angioma or a kaposiform haemangioendothelioma. The key element confirming the fact that the tumour forming the basis of this severe haematological phenomenon differs from that involved in infantile haemangioma is the finding that the GLUT1 immunophenotype is consistently negative in tumours associated with KMS, whereas it is positive in 100% of haemangiomas. Despite frequent confusion in the literature, KMS should be distinguished from chronic intravascular coagulopathy, which is associated with low-flow venous or lymphatic malformations or observed in patients with malignant tumours (angiosarcomas or fibrosarcomas). Differentiation of these two entities is important as the treatments differ significantly. Heterogeneity in the therapeutic response is a characteristic feature of KMS: the response to treatment is unpredictable and as a result the choice of treatment is empirical. Currently, the most frequently effective treatments are general corticotherapy, alpha 2a or 2b interferon therapy, vincristine administration and an antiaggregant combination treatment with ticlopidine and aspirin. Surgical excision, when possible, leads to immediate resolution of the biological phenomena. Therapeutic embolism or radiotherapy are proposed in rare cases as complementary therapies to pharmacological treatment. Platelet transfusions should be avoided as they exacerbate the thrombopaenia and increase the risk of visceral haemorrhage. They are indicated only in cases for which surgical excursion has been programmed and should be carried out just before the intervention as they are consumed within several hours. After resolution of the biological phenomena, the tumours associated with KMS leave only discrete traces: pseudo-fibrosis, a more or less extended red region that is moderately infiltrated and tender, or muscular sequelae. The prognosis for KMS patients has significantly improved but around 10% of cases remain lethal. |