Distribution of HLA-B27 subtypes in ankylosing spondylitis in an Israeli population.

BACKGROUND: The aim of this study was to investigate the contribution of the B27 subtypes to ankylosing spondylitis (AS) expression in a group of Jewish patients from Israel and to compare their distribution with that found in Mexican Mestizo patients. Several HLA-B27 alleles have been clearly associated with AS. Among them, B( *)2705 and B( *)2702 are involved in susceptibility in different populations worldwide. The aim of this study was to investigate the associated subtypes in Israel and to compare the results with Mexican Mestizos, who have Semitic genes as part of their ancestry. METHODS: This is a case/control study that included a group of 24 HLA-B27+ Israeli patients with AS and 51 B27+ healthy subjects, most of them Ashkenazi Jews. The B27 subtypes were characterized using a PCR-SSP method. RESULTS: Only B( *)2702 and B( *)2705 alleles were present in AS patients. However, their allele frequency was not significantly different from that found in the control group, probably because of the small sample size: B( *)2702 (patients 62.5% vs. controls 41.2%, OR = 2.31) and B( *)2705 (patients 37.5% vs. controls 50.9%). Two additional alleles were present only in the controls in low frequency: B( *)2707(5.9%) and B( *)2701(1.9%). It is clear that the major susceptibility allele in Ashkenazi Jews from Israel is B( *)2702. CONCLUSIONS: The only allele conferring risk to AS expression in Israeli Jews was B( *)2702, as was previously described in Mexican Mestizos. Populations of Mediterranean ancestry, such as Latin Americans, should be further explored to understand the contribution of ethnicity to the etiopathogenesis of AS.

Prevalence, causes, and characterization of factor XI inhibitors in patients with inherited factor XI deficiency.

Factor XI deficiency, an injury-related bleeding disorder, is rare worldwide but common in Jews in whom 2 mutations, Glu117Stop (type II) and Phe283Leu (type III), prevail. Mean factor XI activities in homozygotes for Glu117Stop and for Phe283Leu are 1 and 10 U/dL, respectively. Inhibitors to factor XI in patients with severe factor XI deficiency have been reported in a small number of instances. This study was undertaken to determine the prevalence of acquired inhibitors against factor XI in patients with severe factor XI deficiency, discern whether these inhibitors are related to specific mutations, and characterize their activity. Clinical information was obtained from unrelated patients with severe factor XI deficiency, and blood was analyzed for factor XI activity, inhibitor to factor XI, and causative mutations. Immunoglobulin G purified from patients with an inhibitory activity was tested for binding to factor XI, effects on activation of factor XI by factor XIIa and thrombin, and activation of factor IX by exogenous factor XIa. Of 118 Israeli patients, 7 had an inhibitor; all belonged to a subgroup of 21 homozygotes for Glu117Stop who had a history of plasma replacement therapy. Three additional patients with inhibitors from the United Kingdom and the United States also had this genotype and were exposed to plasma. The inhibitors affected factor XI activation by thrombin or factor XIIa, and activation of factor IX by factor XIa. The results imply that patients with a very low factor XI level are susceptible to development of an inhibitor following plasma replacement.