False increased vitamin B12 levels in autoimmune gastritis and subacute combined degeneration of the spinal cord

Due to the fact that vitamin B12 is important in the myelination of the central nervous system, vitamin B12 deficiency is associated with neurologic and psychiatric manifestations. It causes reversible megaloblastic anemia and the most frequent cause of severe vitamin B12 deficiency is the loss of the intrinsic factor in autoimmune atrophic gastritis. Vitamin B12 deficiency can cause both the demyelination of the cervical, dorsal and lateral columns of the spinal cord, and the demyelination of white matter in the brain. We report a case of a 34 year-old man who was admitted in our clinic with ataxic paraparesis and schizoaffective structure with depressive decompensations. Laboratory exams detected a severe hyporegenerative macrocytic anemia and increased values of vitamin B12 (> 2000 pg/mL). Clinical and paraclinical tests that showed improvement under B12 treatment became paradoxical and raised many questions. We found in the literature that it is possible that a false normal vitamin B12 level may have been caused by interference from a high-titer of intrinsic factor antibody. The patient was diagnosed with autoimmune gastritis and secondary loss of intrinsic factor in the gastroenterology department and he had a complete remission of the symptoms and the hematological parameters after vitamin B12 treatment.