AUTOIMMUNE DISORDERS DUE TO DIFICIENCY OF VITAMIN B12

Vitamin B12 (cobalamin) is an essential nutrient found mainly in animal-based foods and functions as a cofactor in two key metabolic reactions. Its absorption and utilization involve multiple steps, including protein release, intrinsic factor-mediated uptake, transport via carrier proteins, and conversion to active forms. Deficiency can lead to hematologic, neurologic, and gastrointestinal symptoms, but diagnosis is challenging due to the limitations of common tests like serum B12, which lack sensitivity and specificity. Newer markers such as holotranscobalamin, methylmalonic acid, and homocysteine offer improved detection but are influenced by other conditions. The lack of a reliable absorption test further complicates accurate diagnosis and treatment planning.