The JAK2(V617F) tyrosine kinase mutation in blood donors with upper-limit haematocrit levels.

BACKGROUND: It is not rare to observe in blood donors a level of haematocrit (Hct) above or close to the highest normal limit. In the case of blood donors the diagnosis and clinical evaluation of this alteration may be complicated by regular blood donations that can mask an underlying disease such as polycythaemia vera. Recently a single acquired mutation in the Janus kinase 2 gene (JAK2) on chromosome 9 was identified and it was found that the incidence of this mutation was high in patients with polycythaemia vera. MATERIAL AND METHODS: From the January 1, 2006 to December 31, 2006 all consecutive donors with a Hct above 50% if males (n=84) and 46% if females (n=19) underwent JAK2 mutation analysis. Seventy-nine donors (59 males and 20 females) whose Hct was normal at their last blood donation were randomly selected and used as controls. RESULTS: Among the group of blood donors with a high Hct, we identified one donor who was positive for the JAK2 mutation. This man had a Hct of 50.6% at his last donation, while his average Hct in the preceding year was 51.7%. The prevalence of the JAK2 mutation could be estimated to be 1%, 0.6% or 0.02% in the three different populations considered: donors with a Hct level above the upper limit of normal, all tested donors or the entire donor cohort attending our transfusion service, respectively. CONCLUSIONS: The present study suggests that apparently healthy subjects with repeatedly high levels of Hct may have the acquired mutation in JAK2. Laboratory screening tests for JAK2 may be offered to blood donors at transfusion services with expertise in molecular genetics.

In vitro reactivity of factor VIII inhibitors with von Willebrand factor in different commercial factor VIII concentrates.

A relevant aspect in the treatment of patients with hemophilia A (HA) presenting inhibitor against factor VIII (FVIII) is the different antigenicity of FVIII used for replacement therapy. The aim of the study was to assess the effect of different products, with variable von Willebrand factor (vWF) concentration, in preventing the binding of inhibitor to FVIII. The reactivity of inhibitors from plasma of 18 patients with HA versus three commercial concentrates containing different amounts of vWF was compared. The results show that increasing amounts of vWF might have a protective effect on the transfused FVIII inactivation.

The Italian haemophilia B mutation database: a tool for genetic counselling, carrier detection and prenatal diagnosis.

INTRODUCTION: The Italian database of factor IX gene (F9) mutations has been built since 2001 and is, so far, the most practical instrument for comprehensive genetic counselling, carrier detection and prenatal diagnosis. Over time the haemophilia B database has been enriched by entries on a larger number of patients and molecular genetic data identifying heterogeneous mutations spanning the entire F9. METHODS: Conformation sensitive gel electrophoresis is a variant of heteroduplex analysis, which has been applied for screening F9 for mutations, which are further fully characterised by direct sequencing of the amplified mutated regions. This project has involved 29 Italian haemophilia centres and provides data concerning the analysis of a cohort of 306 unrelated patients with haemophilia B (191 with severe, 67 with moderate and 48 with mild disease, including 8 patients with severe haemophilia B with inhibitors). The recorded data include levels of factor IX clotting activity, inhibitor status and clinical severity. RESULTS: Detailed analysis of the mutations revealed 164 different mutations, that are considered as unique molecular events (8 large deletions, 11 small deletions, 1 combined deletion/ insertion, 2 insertions, 104 missense, 20 nonsense, 14 mutations in a splicing site, 3 in the promoter and 1 silent). The data recorded in the Italian F9 mutation database provided the basis to study 85 families with haemophilia B, involving 180 females (20 obligate carriers, 106 carriers and 54 non-carriers) and enabled 14 prenatal diagnoses to be made in 12 females. CONCLUSIONS: Genetic analysis is required to determine female carrier status reliably. Female relatives may request carrier analysis, when a male relative is first diagnosed as having haemophilia or when they are pregnant. At present, the data collected in the Italian national register of mutations in haemophilia B provide the opportunity to perform prompt and precise determination of carrier status and prenatal diagnosis by specific mutation analysis.