Pernicious Anemia

A condition in which the body cannot make enough red blood cells due to a deficiency in vitamin B12. Pernicious anemia is somewhat more common in people with Type 1 diabetes than it is in the general population.

Pernicious anemia is most commonly caused by an autoimmune attack on the parietal cells of the stomach. Ordinarily, the parietal cells make a protein called intrinsic factor, which helps the body absorb vitamin B12. When the parietal cells get destroyed by the immune system, they can no longer make intrinsic factor, and vitamin B12 cannot be absorbed properly. Lack of vitamin B12 keeps red blood cells from dividing normally and causes them to become too large, so that they have difficulty getting out of the bone marrow. Vitamin B12 is also necessary for the nervous system to work properly.


Pernicious anemia can cause multiple problems throughout the body. In people with pernicious anemia, the heart has to work harder to pump enough blood to nourish the body’s tissues. This can lead to cardiac arrhythmias (fast or irregular heartbeats), an enlarged heart, and even heart failure (in which the heart cannot pump blood efficiently enough to meet the body’s needs). It may also raise the risk of heart attacks and strokes. Related damage to the nervous system can cause such diverse symptoms as numbness and tingling in the hands and feet, difficulty with balance, vision changes, memory loss, and confusion. Other symptoms include fatigue, loss of appetite, and diarrhea.

Fortunately, pernicious anemia is usually easy to treat with vitamin B12 injections, although some people develop permanent nerve damage before the condition is diagnosed and treated. In addition to pernicious anemia, there are a number of other autoimmune diseases that tend to run in clusters in people with Type 1 diabetes, including Graves disease (in which autoantibodies stimulate the thyroid gland to produce too much thyroid hormone), Hashimoto thyroiditis (in which the immune system attacks the thyroid gland, causing it to secrete less and less thyroid hormone and slow down certain bodily functions), and Addison disease (in which the immune system attacks the outer layer of the adrenal glands, causing them to secrete less of their hormones and leading to such problems as weight loss, muscle weakness, and low blood pressure).