The Role of the Clinical Laboratory in Nutritional Assessment
Aruna Bakhru in Nutrition and Integrative Medicine, 2018
Deficiencies of vitamin B12 and folate are common causes of macrocytic anemia.103 Pernicious anemia, a type of vitamin B12 anemia, is caused by insufficient production of intrinsic factor. Pernicious anemia typically occurs at 60 years of age or older.104 The etiology of vitamin B12 deficiency is diverse and includes lack of intrinsic factor, altered pH in the small intestine, and lack of absorption of B12 complexes in the terminal ileum. As with folate deficiency, poor intake of leafy vegetables can cause vitamin B12 deficiency. Other foods rich in vitamin B12 include eggs, dairy products, fortified cereal or soy beverages, tempeh, and miso (tempeh and miso are foods made from soybeans). Atrophy or loss of the gastric mucosa can prevent vitamin B12 absorption. Bacterial overgrowth in the intestine can lead to bacteria competing for cobalamin. Bowel resection and tapeworm infections, such as with Diphyllobothrium latum, also can lead to vitamin B12 deficiency.
Personalization of Nutrition Advice
David Heber, Zhaoping Li in Primary Care Nutrition, 2017
Vitamin B12, also called cyanocobalamin, is needed to make red blood cells and is necessary for the synthesis of nerve sheaths, fatty acids, and DNA. Since this vitamin is stored in the liver, nutritional deficiency usually takes years to develop. It is much more common to see metabolic deficiencies. Most commonly, an anemia due to B12 deficiency results from an autoimmune disease called pernicious anemia, in which the parietal cells in the stomach that make a binding protein (intrinsic factor) necessary for B12 absorption are destroyed (Seetharam and Alpers 1982). The healthy individuals most at risk of a dietary vitamin B12 deficiency are vegetarians, since there is no B12 in any plant product. There is also a decreased capability for absorption of vitamin B12 in the elderly due to decreased gastric acid secretion (Carmel 1997).
The Hematologic System and its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
Iron is not the only deficiency that causes anemia. Deficiency of vitamin B12 or folic acid can impair the production of erythrocytes, creating cells that grow slowly with many fewer divisions. The resulting cells are abnormally large (macrocytic), oddly shaped, and extremely fragile. Macrocytic anemia is often easily treated with supplementation of the deficient nutrient. One form of this condition is pernicious anemia, in which a deficiency of vitamin B12 is caused by an inability of the gastric mucosa to secrete intrinsic factor, a substance that facilitates B12 absorption. Pernicious anemia may result from atrophic gastritis, gastrectomy, or myxedema. Diagnosis may include evaluation of radioactive Bi2 absorption with and without exogenously administered intrinsic factor (Schilling test).
Rare anterior funiculus lesions in subacute combined degeneration of the spinal cord: a case report and literature review
Published in International Journal of Neuroscience, 2020
Lei Wu, Bingxin Shi, Mangsuo Zhao, Hui Sun, Fangfang Zhang, Jie Li, Dehui Huang, Zhen Shi
Pernicious anemia is a common cause of vitamin B12 deficiency. Many patients with chronic atrophic gastritis have autoantibodies to parietal cells and/or intrinsic factors [6], and the low levels of gastric acid can stimulate gastrin secretion. High gastrin levels then promote proliferation of both neuroendocrine cells and nonspecialized epithelial cells, which may eventually lead to development of gastric carcinoid tumors and other carcinomas. Thus, pernicious anemia is sometimes accompanied by gastric cancer [7]. In the present case, the patient’s echo-gastroscopic finding suggests a carcinoid tumor concomitant with chronic gastritis, which reasonably explain the presence of intrinsic factor antibodies and decreased vitamin B12 levels. Together with the megaloblastic anemia, elevated serum homocysteine, and notable effectiveness of vitamin B12 supplementation, her diagnosis of SCD is further verified. In a broad sense, her SCD can be explained by a paraneoplastic vitamin B12 deficiency, which is mediated by intrinsic factor antibody [8, 9].
Pernicious anemia: a myelodysplastic syndrome look-alike
Published in Journal of Community Hospital Internal Medicine Perspectives, 2019
Yazeed Kesbeh, Zahra Pakbaz
When there is an unclear reason as to why the patient would be B12 deficient, the clinician should suspect pernicious anemia, which is the most common cause of B12 deficiency [1]. Pernicious anemia is an autoimmune cause of B12 deficiency [6,8,9]. Testing for anti-intrinsic factor antibodies is a specific means to confirm the patient has pernicious anemia [1,6]. If the clinical picture and labs do not point to the same diagnosis, or the results of specific diagnostic tests are not available in a timely manner (as in this case) it is safe to empirically administer Vitamin B12 and assess the bone marrow response, evident by an increasing reticulocyte count and hemoglobin level [10]. If a patient receives empiric B12 treatment, anti-intrinsic factor antibodies should be checked at least one week after holding B12 supplementation to avoid a false positive result [1]. Also, it is important to consider that patients with anti-intrinsic factor antibodies can have falsely elevated B12 levels due to the autoantibodies’ ability to interfere with the test reagents [11–13], which possibly occurred in this case.
Nitrous oxide abuse induced subacute combined degeneration despite patient initiated B12 supplementation
Published in Clinical Toxicology, 2022
Courtney Temple, B. Zane Horowitz
N2O results in analgesic, anxiolytic and dissociative effects. The anesthetic action results from noncompetitive inhibition of the NMDA glutamate receptors [4] and the antinociceptive action is produced by opioid release in the midbrain modulating pain processing in the spinal cord [5,6]. Deficiency of Vitamin B12 is typically suspected in patients who present with unexplained macrocytosis with or without the presence of anemia, or neurologic symptoms. It is often described in patients with dietary restrictions or malabsorptive conditions such as pernicious anemia. Chronic N2O abuse usually manifests first with neurotoxicity rather than hematologic disturbance and up to a third of patients with neurologic symptoms have no evidence of hematologic abnormalities [7,8].
Related Knowledge Centers
- Ataxia
- Fatigue
- Reflex
- Shortness of Breath
- Vitamin B12
- Vitamin B12 Deficiency
- Vomiting
- Nausea
- Pallor
- Red Blood Cell
- Shortness of Breath