Langerhans cell histiocytosis is a rare haematological disorder with variable clinical findings and a high mortality rate. On the other hand, Kasabach-Merritt syndrome is of rare onset at adult age, requiring the simultaneous presentation of vascular lesion, thrombocytopenia, and consumptive coagulopathy. We present the first reported case of both diseases in a single patient and highlight the difficulties of diagnostic. A 69-year-old woman with immune thrombocytopenic purpura underwent surgery for the removal of giant skin haemangiomas. During post-operative care, intravascular disseminated coagulopathy developed. After weeks of corticosteroids and immunosuppressive therapy with no clinical improvement, pulmonary tuberculosis was diagnosed and appropriate treatment initiated. Despite all the efforts, the patient's clinical condition kept worsening and she eventually died. An autopsy revealed bone marrow Langerhans cell histiocytosis. In this case, the patient's autoimmune background together with tuberculosis and intravascular disseminated coagulopathy masked the presentation and made the diagnosis of a rapidly progressive fatal disease very difficult.