SummaryIt is unusual to find many mast cells in the bone marrow. It has been reported in cases of primary and secondary panmyelophtisis, of aplastic anemia, of lymphatic leukemia. We found a large number of mast cells in the hone marrow of a young female aged 21, with hemorrhagic diathesis and splinomegaly since leucopenia, bleeding tendency and infantilism.To our knowledge no similar case has been reported until now.The heparin content of the blood of this patient was within normal limits.