Patients with systemic mastocytosis (SM) can suffer from disabling symptoms related to mast cell mediator release or mast cell infiltration, requiring mast cell eradication. In the present absence of any curative therapy, a recent case report describing the efficacy of cladribine showed promising results. In a pilot study, the efficacy of cladribine (0.10-0.13 mg/kg in a 2-hour infusion, days 1-5; repeated at 4-8 weeks until 6 cycles) was studied. Ten patients with SM with severe symptoms were treated. Four patients were classified as having indolent or smoldering mastocytosis, 3 as having aggressive systemic mastocytosis, and 3 as having SM with an accompanying hematologic malignancy. Nine patients received 6 courses, 1 patient stopped because of toxicodermia. All responded concerning signs, symptoms, and mast cell parameters (serum tryptase and urinary histamine metabolite excretion), although none achieved a complete remission. Prolonged follow-up is required, as response is ongoing in most cases. One patient relapsed within 11 months and showed a second response. Side effects were mainly related to bone marrow suppression. Single-agent cladribine is an effective and relatively safe treatment for severe systemic mastocytosis. The optimal dose and schedule need to be explored.

SummaryHyperhomocysteinemia is an established risk factor for atherosclerosis and vascular disease. Until the early nineties the relationship with venous thrombosis was controversial. At this moment ten case-control studies on venous thrombosis are published. We performed a meta-analysis of these reports.We performed a MEDLINE-search from 1984 through June 1997 on the keywords “homocysteine” or “hyperhomocysteinemia” and “venous thrombosis”, which yielded ten eligible case-control studies.We found a pooled estimate of the odds ratio of 2.5 (95% CI 1.8-3.5) for a fasting plasma homocysteine concentration above the 95th percentile or mean plus two standard deviations calculated from the distribution of the respective control groups. For the post-methionine increase in homocysteine concentration we found a pooled estimate of 2.6 (95% CI 1.6-4.4).These data from case-control studies support hyperhomocysteinemia as a risk factor for venous thrombosis. Further research should focus on the pathophysiology of this relationship and on the clinical effects of reducing homocysteine levels by vitamin supplementation.

Please be advised that this information was generated on 2018-05-12 and may be subject to change.11 Snyder PJ, Utiger RD. Response to thyrotropin-releasing hormone (TRH) in normal man. J Clin Endocrinol Metab 1972; 34: 380-85. 12 Rooney S, Marino P, Gobrau L, Gross I, Warshaw J. Is hyperhomocysteinaemia a risk factor for recurrent venous thrombosis? M artin den Heijer, Henk J Biom , Wim B J G errits, F rits R Rosendaai, Hans L H aak, P ie rre W W ijerm ans, Gerard M J Bos SummarySeveral studies have shown a relation between » hyperhomocysteinaemia and arterial vascular disease. We looked at the association between hyperhomocysteinaemia and venous thrombosis which could be clinically important as hyperhomocysteinaemia is easily corrected by vitamin supplementation.We studied 185 patients with a history of recurrent venous thrombosis and 220 controls from the general population. Homocysteine concentrations were measured before and 6 h after oral methionine loading. We defined hyperhomocysteinaemia as the homocysteine concentration above the fasting or the postmethionine value found for the 90th percentile of the controls. Of the 185 patients with recurrent thrombosis, 46 (25%) had fasting homocysteine concentrations above the 90th percentile or the controls (odds ratio is 3-1 [1-8-5-5]). After adjustment for age, sex, and menopausal status the odds ratio was 2-0 (l-5-2*7). Similar results were found for the post-methionine value (unadjusted odds ratio 3-1 [1-7-5-5], adjusted 2*6 [1-9-3-5]).Hyperhomocysteinaemia is a common risk factor for recurrent venous thrombosis and can lead to a two-fold or three-fold increase in risk.

The Vitamins and Thrombosis (VITRO) study investigated the effect of homocysteine lowering by daily supplementation of B vitamins on the risk reduction of deep vein thrombosis (DVT) and pulmonary embolism (PE). Patients between 20 to 80 years old with a first objectively confirmed proximal DVT or PE in the absence of major risk factors and a homocysteine concentration above the 75th percentile of a reference group were asked to participate (hyperhomocysteinemic group). A similar study was conducted in a random sample of patients with a homocysteine below the 75th percentile of the reference group (normohomocysteinemic group). After informed consent was obtained, patients were randomized to daily multivitamin supplementation (5 mg folic acid, 50 mg pyridoxine, and 0.4 mg cyanocobalamin) or placebo and were followed for 2.

SummaryVenous thrombosis is a multicausal disease involving acquired and genetic factors. In this study we investigated a possible interaction between hyperhomocysteinemia (fasting or postload) and factor V Leiden or prothrombin G20210A on the risk of recurrent venous thrombosis. We also looked at the risk due to mutations in the MTHFR-gene (C677T and A1298C).We performed a case-control study in 171 patients with a history of recurrent venous thrombosis and 461 control subjects from the general population. Hyperhomocysteinemia (fasting or 6 h after an oral methionine load) was defined as a homocysteine concentration above the 90th percentile of the distributions in the control group.The odds ratio (adjusted for age and sex) for recurrent venous thrombosis was 1.8 (95%CI: 1.1 to 3.0) for fasting hyperhomocysteinemia, 5.1 (95%CI: 3.0 to 8.6) for factor V Leiden and 1.8 (95%CI: 0.7 to 4.2) for prothrombin G20210A. We found 14 patients and 3 controls with both hyperhomocysteinemia and factor V Leiden, which yielded an odds ratio of 11.6 (95%CI: 3.2 to 42.5). We found no interaction between hyperhomocysteinemia and prothrombin G20210A. The relative risk for MTHFR 677CT was 1.6 (95%CI: 1.1 to 2.4) and for MTHFR 677TT was 1.4 (95%CI: 0.7 to 2.8). The combined risk for MTHFR 677TT and factor V Leiden was 18.7 (95%CI: 3.3 to 108).We conclude that hyperhomocysteinemia and factor V Leiden are risk factors for recurrent venous thrombosis. The risk of thrombosis appeared high for individuals who had both risk factors.