Malignant (acute) myelosclerosis--a clinical and pathological study in 6 patients

Clinical and morphological findings are described in 6 patients with malignant (acute) myelosclerosis/fibrosis (MMS). Haematological data are characterized by severe anaemia and thrombocytopenia, frequently accompanied by a leucopenia with an increase in myeloblasts and promyelocytes in the peripheral blood count. There is an absence of, or a minimal hepatosplenomegaly and the survival times after onset of clinical symptoms to death range from 4-12 months. The histopathology of the bone marrow shows a conspicuous proliferation of blasts (myeloblasts, promyelocytes and megakaryoblasts) in a variable amount, besides a fibrosclerosis consisting of reticulin and collagen fibrils. A comparison of MMS with ordinary myelofibrosis/osteomyelosclerosis (MF/OMS) of a chronic course implicates two important facts: (a) evolution of fibrosclerosis takes a considerable period of time for manifestation, which ranges between 20-30 months; (b) the histopathology of MMS is identical with those features observable in the rare event of a terminal stage, i.e. blastic transformation of chronic MF/OMS. Consequently MMS should be designated as an accelerated variant of MF/OMS with a rather early occurrence of a blastic crisis. The insidious onset with the dominant clinical finding of anaemia is probably responsible for the relatively late appearance of symptoms, while the progressive course prevents an overt myeloid metaplasia with a massive hepatosplenomegaly.