I just found this little gem:
Pernicious anemia is a type of autoimmune anemia that is caused by the body’s inability to absorb vitamin B 12. The body produces antibodies that attack the intrinsic factor and the parietal cells. Parietal cells are found in the stomach lining. They produce intrinsic factor, which is a glycoprotein that enables the small intestine to process vitamin B 12. This anemia is the most common blood disorder.
Symptoms of pernicious anemia are due to the lack of B 12 and include sore tongue, mouth ulcers, mental fogginess, fatigue, joint pain and tinnitus.