Low B12 levels in chronic idiopathic urticaria.

Recent studies suggest that autoimmune mechanisms may be involved in the etiology of chronic idiopathic urticaria (CIU). There is a higher prevalence of B12 deficiency in autoimmune diseases and possibly in gastric Helicobacter pylori (H. pylori) infection. The frequency of B12 deficiency in CIU is unknown. Our objective in this study was to determine the prevalence of B12 deficiency in patients with CIU and also its relationship to gastric H. pylori infection and serologic markers of autoimmunity in these groups. Thirty-three patients with CIU and 27 healthy controls were included in the study. Serum vitamin B12 levels, H. pylori infection and serological markers of autoimmunity (anti-thyroglobulin, thyroid microsomal, gastric parietal cell and antinuclear autoantibodies) were investigated. H. pylori infection was determined according to serology and gastric biopsy in 19 patients, serology and urea breath test in 4 patients and serology alone in the remaining 10 patients. Serum B12 levels were below the normal reference range in 11/33 (33.3%) patients with CIU. The mean serum B12 levels among patients with CIU and the controls were 281+/-127.5 pg/ml and 465.1+/-140.3 pg/ml (p=0.0001), respectively. Anti-thyroid antibodies were positive in 6 of 11 patients (54.5%) with low B12 levels, but only in 4 of 27 (14.8%) healthy controls (p=0.019). Anti-GPC antibodies were positive in 4 of 11 (36.4%) patients with CIU and low B12 levels, but only in 2 of 27 (7.4%) healthy controls (p=0.047). In CIU patients, there was no difference in the frequency of IgG H. pylori antibodies between those with low B12 levels and normal B12 levels. Among the 19 patients who had been performed gastric endoscopy, 15 patients (78.9%) had chronic antral gastritis, 2 patients (10.5%) had atrophic gastritis and there were normal findings in 2 patients (10.5%). In conclusion, serum B12 levels were found to be below the normal reference range in 33% of the patients with CIU. An association between low B12 levels and H. pylori could not be shown. The higher frequency of antithyroid and anti-GPC antibodies in patients with low B12 levels suggest that low B12 levels in CIU may be autoimmune in nature.