Association of common variable immunodeficiency with vitamin B6 deficiency

Objective: To study the prevalence of vitamin B-6 deficiency in common variable immunodeficiency and the impact of vitamin B-6 supplementation on immune function in the disorder. Design: Open, non-blinded. Setting: Medical School Hannover, Hannover, Germany. Subjects: Plasma vitamin B6 concentrations were measured in all the 54 common variable immunodeficiency (CVID) patients visiting our outpatients' clinics in 2005. Interventions: The 17 patients with a decreased vitamin B-6 concentration were recommended to take 50 mg of vitamin B-6/day for 3 months. Then, vitamin B-6 concentrations, absolute number of lymphocyte populations and immunoglobulin concentrations were controlled. Results: Vitamin B6 concentrations were reduced in 17/54 patients. All 11/17 patients following our advice to substitute vitamin B-6 had normal vitamin B-6 plasma concentrations 3 months later. In parallel, the number of CD4+ T cells significantly increased. In contrast, concentrations of serum immunoglobulins were not improved. Conclusions: Vitamin B-6 deficiency is common in CVID. The vitamin deficiency is not the cause of CVID and vitamin supplementation does not relieve humoral immunodeficiency. Nevertheless, vitamin B6 should be measured in CVID to avoid possible long-term complications of its deficiency.