Kasabach-Merritt phenomenon (KMP) is a rare life-threatening vascular condition of infancy. Prognosis factors and long-term follow-up data are lacking. We retrospectively analysed the records of 24 infants (10 females, 14 males) treated for KMP in the Department of Dermatology of Necker-Enfants Malades Hospital, Paris, France, from 1984 to 2012. Mean duration of thrombocytopaenia (2,000-38,000 platelets/mm3, mean 10,500/µl) was 8.8 months (range 3 days-84 months), which correlated with tumour infiltration depth on imaging. D-dimer levels were always elevated, even before KMP onset. Each patient received a mean of 4.8 different treatments (range 1-10). Median follow-up was 6.5 years (range 2 months-22 years). All infants had residual cutaneous lesions, along with inflammatory manifestations (n = 9), elevated D-dimer (n = 5) and orthopaedic sequelae (n = 5). The permanent coagulopathy (elevated D-dimer) even after resolution of KMP suggests the presence of chronic low-grade platelet trapping, with possible sudden worsening, and raises the possibility of prophylactic anti-platelet therapy.