Vitamin B12 Deficiency
Autoimmune and Other Causes of Cobalamin Deficiency
Vitamin B12 deficiency can cause a variety of symptoms, including dementia. Autoimmune causes of this deficiency include pernicious anemia and autoimmune gastritis.
Vitamin B12
Vitamin B12, which is the common name for cobalamin, is an essential vitamin obtained from dietary sources. Vitamin B12 deficiency is present in 1 to 3 percent of the population, although the incidence of vitamin B12 deficiency rises dramatically with age. Among people older than 60 years, the incidence of cobalamin deficiency is as high as 10 to 30 percent. This incidence is expected to increase in the next 20 years. Cobalamin deficiency is caused by diets low in vitamin B12, malabsorption syndromes, infection, and the autoimmune disorders autoimmune gastritis and pernicious anemia. Vitamin B12 deficiency is treated with either oral or intramuscular injections of vitamin B12.
Symptoms and Signs of Vitamin B12 Deficiency
A number of unrelated symptoms can occur in vitamin B12 deficiency. Clinical manifestations of vitamin B12 deficiency include:
- Hematological changes, such as megaloblastic anemia (characterized by large red blood cells), and a low production of other blood cell types, which is known as pancytopenia. Types of pancytopenia seen in vitamin B12 deficiency include leucopenia (low white blood cell levels), thrombocytopenia (low platelet count), and anemia.
- Neurologic changes, including paresthesias, peripheral neuropathy and combined systems disease such as demyelination (loss of protective outer sheath) of the dorsal columns of the nerve cells in the spine.
- Psychiatric changes, including irritability, personality change, mild memory impairment, dementia, depression, and psychosis.
- Cardiovascular symptoms, including a possible increased risk of heart attack and stroke.
During its absorption vitamin B12 binds to the protein haptocorin found in saliva. In the duodenum, vitamin B12 is released from haptocorin. The free cobalamin molecules are then linked to a substance known as intrinsic factor in the proximal ileum of the intestines. In this form vitamin B12 enters the mucosal cells that line the intestines. Here, cobalamin is released. In its free form it binds to the protein transcobalamin, and in this form vitamin B12 is released into the blood circulation. Within the body’s cells vitamin B12 is freed from transcobalamin protein and it acts as a coenzyme for the synthesis for various enzymes needed for DNA synthesis and energy production.
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