Benzene-associated myelofibrosis

Shanghai Health Study (2001-2009): What was learned about benzene health effects?

The Shanghai Health Study (SHS) was a large epidemiology study conducted as a joint effort between the University of Colorado and Fudan University in Shanghai, China. The study was funded by members of the American Petroleum Institute between 2001 and 2009 and was designed to evaluate the human health effects associated with benzene exposure. Two arms of the SHS included: an occupational-based molecular epidemiology study and several hospital-based case control studies. Consistent with historical literature, following sufficient exposure to relatively high airborne concentrations and years of exposure, the SHS concluded that exposure to benzene resulted in an increased risk of various blood and bone marrow abnormalities such as benzene poisoning, aplastic anemia (AA), myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML). Non-Hodgkin lymphoma (NHL) was not significantly increased for the exposures examined in this study. Perhaps the most important contribution of the SHS was furthering our understanding of the mechanism of benzene-induced bone marrow toxicity and the importance of identifying the proper subset of MDS relevant to benzene. Investigators found that benzene-exposed workers exhibited bone marrow morphology consistent with an immune-mediated inflammatory response. Contrary to historic reports, no consistent pattern of cytogenetic abnormalities was identified in these workers. Taken together, findings from SHS provided evidence that the mechanism for benzene-induced bone marrow damage was not initiated by chromosome abnormalities. Instead, chronic inflammation, followed by an immune-mediated response, is likely to play a more significant role in benzene-induced disease initiation and progression than previously thought.

Idiopathic myelofibrosis: pathogenesis to treatment

Idiopathic myelofibrosis (IMF) is the least common of the chronic myeloproliferative disorders and carries the worst prognosis with a median survival of 4 years. It is a clonal haematopoietic stem-cell disorder and, although the pathogenesis remains unclear, approximately 50% of cases are known to possess an activating JAK2 V617F mutation. In contrast, the characteristic stromal proliferation is a reactive, or secondary, event that results from the aberrant release of a variety of growth factors from megakaryocytes and monocytes. Treatment for most cases is supportive, although androgens, recombinant erythropoietin, steroids and thalidomide are effective modalities for the amelioration of anaemia. Myelosuppression, splenectomy and irradiation are valuable therapeutic modalities for specific clinical situations. Prognostic scores are available to aid the identification of cases for whom bone marrow transplantation should be considered. Recently, the use of reduced intensity conditioning has resulted in prolonged survival and lower transplant-related mortality. This review summarises the recent advances in the disease's pathogenesis and discusses the role of the various therapeutic options.

Pathogenesis and management of idiopathic myelofibrosis

Idiopathic myelofibrosis is the least common and carries the worst prognosis of the chronic myeloproliferative disorders. The primary disease process is a clonal haematopoietic stem cell disorder which results in a chronic myeloproliferation and an atypical megakaryocyte hyperplasia. In contrast, the characteristic stromal proliferation is a reactive phenomenon, resulting from the inappropriate release of megakaryocyte/platelet-derived growth factors, including PDGF, TGF-beta bFGF and calmodulin. The median survival is approximately 4 years, although individual survival varies greatly. A variety of prognostic schema have been developed which enable the identification of high-risk patients, for whom bone marrow transplantation should be considered. Management for the majority of patients, however, is directed towards the alleviation of symptoms and improvement in quality of life. This review summarizes the recent advances in our understanding of the disease's pathogenesis and discusses the limited therapeutic options available to clinicians.

High incidence of myeloproliferative disorders in Ashkenazi Jews in northern Israel

We have analysed epidemiological parameters in 339 patients with myeloproliferative disorders (MPD) diagnosed in northern Israel between 1975 and 1989 as having polycythemia vera (191 patients), agnogenic myeloid metaplasia (AMM) (113) and essential thrombocythemia (ET) (36). Mean average annual incidence was 11.4 per 1 million residents for polycythemia vera, 6.5 for AMM and 2.1 for ET. For all three diseases the average annual incidence increased with age and was 10 times higher in patients over 65 years compared to those less under the age of 45 years. Four percent of all patients had relatives with MPD. Incidence of MPD in Jews was 10 fold higher than expected compared to Arabs and this difference was noted for all 3 diseases. The incidence in Ashkenazi Jews originating from eastern and central Europe, was 10 and 20 folds higher than in Sephardic Jews and Arabs respectively. Mean age at diagnosis of MPD in Arabs and Sephardic Jews was lower than in Ashkenazi Jews (52 and 56 years compared to 64 years P < 0.05). Likewise, mean age at diagnosis was lower in the 11.5% of MPD patients with prior exposure to biological or chemical hazards compared to unexposed individuals (58 years versus 63 years, P < 0.02). These data demonstrate a cluster of MPD in Ashkenazi Jews in northern Israel and emphasize the importance of genetic predisposition possibly interacting with acquired factors in the pathogenesis of these disorders.

Myelofibrosis and focal segmental glomerulosclerosis associated with toluene poisoning

A 60-year-old man with long-term exposure to toluene presented with both myelofibrosis and focal segmental glomerulosclerosis. There was also evidence of other toluene-related complications to support the diagnosis of toluene toxicity. The toxic effects of toluene, particularly kidney disorders and haematotoxicity, suggest a relationship between toluene, myelofibrosis and focal segmental glomerulosclerosis.