Cobalamin deficiency can mask depleted body iron reserves.

Vitamin B12 deficiency impairs DNA synthesis and causes erythroblast apoptosis, resulting in anaemia from ineffective erythropoiesis. Iron and cobalamin deficiency are found together in patients for various reasons. We have observed that cobalamin deficiency masks iron deficiency in some patients. We hypothesised that iron is not used by erythroblasts because of ineffective erythropoiesis due to cobalamin deficiency. Therefore, we aimed to demonstrate that depleted iron body reserves are masked by cobalamin deficiency. Seventy-five patients who were diagnosed with cobalamin deficiency were enrolled in this study. Complete blood counts and serum levels of iron, unsaturated iron binding capacity (UIBC), ferritin, vitamin B12, and thyroid stimulant hormone were determined at diagnosis and after cobalamin therapy. Patients who had a combined deficiency at diagnosis and after cobalamin therapy were recorded. Before cobalamin therapy, we found increased serum iron levels (126.4 ± 63.4 µg/dL), decreased serum UIBC levels (143.7 ± 70.8 µg/dL), increased serum ferritin levels (192.5 ± 116.4 ng/mL), and increased transferrin saturation values (47.2 ± 23.5 %). After cobalamin therapy, serum iron levels (59.1 ± 30 µg/dL), serum ferritin levels (44.9 ± 38.9 ng/mL) and transferrin saturation values (17.5 ± 9.6 %) decreased, and serum UIBC levels (295.9 ± 80.6 µg/dL) increased. Significant differences were observed in all values (p < 0.0001). Seven patients (9.3 %) had iron deficiency before cobalamin therapy, 37 (49.3 %) had iron deficiency after cobalamin therapy, and a significant difference was detected between the proportions of patients who had iron deficiency (p < 0.0001). This study is important because insufficient data are available on this condition. Our results indicate that iron deficiency is common in patients with cobalamin deficiency, and that cobalamin deficiency can mask iron deficiency. Therefore, we suggest that all patients diagnosed with cobalamin deficiency should be screened for iron deficiency, particularly after cobalamin therapy.