Pernicious anemia is an autoimmune condition that may go undiagnosed for years, according to a review by Dr. Edith Lahner and Dr. Bruno Annibale of the University Sapienza in Italy. It starts with inflammation of the stomach lining. This may initially be caused by an infection of H. pylori or other pathogens, but the immune system's attack on the gastric mucosa continues after the infection is “burned out”. The result is called atrophic body gastritis. This damage impairs the stomach's ability to produce stomach acid as well as two proteins called gastrin and intrinsic factor.
Vitamin B12 normally binds to intrinsic factor, and the combination can be absorbed by the intestines. When gastritis reduces the production of intrinsic factor, a vitamin B12 deficiency develops even though there may be plenty in the diet. Red blood cells need this vitamin for their development, so the deficiency causes anemia.
Pernicious anemia develops very slowly in most patients. Symptoms of poor digestion and anemia evolve gradually, so that patients get used to them and fail to seek treatment. Gastrointestinal symptoms include bloating and fullness after meals, early satiety, and discomfort. Symptoms related to the loss of red blood cells include weakness, decreased mental concentration, headache, heart palpitations, chest pain, unsteady gait, clumsiness, muscle spasticity, and abnormal sensations such as pins and needles.
The treatment is injections of vitamin B12. These may be given daily, then weekly, then monthly or less often. The earlier treatment is started, the less chance of long-term consequences. Patients with pernicious anemia should be monitored for gastric cancer, according to Lahner and Annibale.
Bone loss is another concern. Dr. Nathan A. Merriman and collaborators at the University of Pennsylvania School of Medicine reported that patients with pernicious anemia have an increased risk of hip fracture. There are several mechanisms for this:
1. Vitamin B12 deficiency may cause peripheral neuropathy, which increases the risk of falling
2. Vitamin B12 deficiency interferes with bone health