- Cobalamin is necessary for DNA synthesis and is found in sardines, shrimp, calf’s liver, and other animal meats.
- Cobalamin is released from food by gastric peptidases and is then absorbed in the ileum through intrinsic factor.
- Because of the large hepatic reservoir and efficient reuptake by the enterohepatic system, cobalamin deficiency due to decreased PO intake takes several years to develop.
- Malabsorption – pernicious anemia, inflammatory bowel disease, celiac disease, bacterial overgrowth, pancreatic insufficiency
- Pernicous anemia is due to antibodies directed at hydrogen potassium adenosine triphosphatase in the parietal cell membrane causing parietal cell atrophy and reduced intrinsic factor levels
- Glossitis, weight loss, pale yellow skin, abdominal pain secondary to gastritis
- Loss of vibration and propioception which can progress to spastic ataxia, hallucinations, dementia, psychosis
- Peripheral smear can show hypersegmented neutrophils, basophilic stippling, oval macrocytes
- Hemolysis, thrombocytopenia, and leukopenia are other common lab findings due to inefficient hematopoiesis
- Elevated homocysteine and methylmalonic levels; high methylmalonic levels are more sensitive and specific in diagnosing cobalamin deficiency than actual cobalamin levels
- Parental: 1000mcg daily for 1 week, 1000mcg once a week for 4 weeks, 1000mcg every month for rest of life
- Oral: 1000mcg-2000mcg PO every day. Recent research has shown PO regimens to be comparable to parental as it is thought that the presence of a second, lower efficiency transport system for cobalamin which does not require intrinsic factor or a functioning terminal ileum can be utilized