Epidemiology
PA is estimated to affect 0.1% of the general population and 1.9% of those over 60, accounting for 20–50% of B12 deficiency in adults. A review of literature shows that the prevalence of PA is higher in Northern Europe, especially in Scandinavian countries, and among people of African descent, and that increased awareness of the disease and better diagnostic tools might play a role in apparently higher rates of incidence. History
A case of anemia with a first recognition of associated atrophic gastritis a feature of pernicious anemia, was first described in 1824 by James Combe. This was fully investigated in 1849, by British physician Thomas Addison, from which it acquired the common name of Addisons anemia. In 1871, the first accurate description of the disease in Europe was by Michael Anton Biermer, a German physician who referred to the insidious course of the condition, and because it was untreatable and fatal at the time, he first referred to it as "pernicious" anemia. In 1900 Russell coined the term subacute combined degeneration of spinal cord.In 1907, Richard Clarke Cabot reported on a series of 1200 patients with PA; their average survival was between one and  three years. Pernicious anemia was a fatal disease before about the year 1920, until the importance of the liver in hematopoiesis was recognized, the treatment of pernicious anemia was unsuccessful and arbitrary. It may have motivated George Whipple, who had a keen interest in liver diseases, to investigate the livers role in hematopoiesis.
Whipple began evaluating the effects of treatments for anemia caused by chronic blood loss. Whipple, Huber, and Robchett have studied the effects on hemoglobin and blood regeneration of a variety of treatments – among which only raw liver has shown real promise. Serendipity is said to have played a role in this discovery. Whipple observed that blood regeneration was poor in dogs fed cooked liver after chronic blood loss, had it not been that a lazy laboratory technician had given the dogs raw liver, the much more dramatic response might not have been discovered at that point in history. Around 1926, George Minot and William P. Murphy, who learned of Whipples discovery, sought raw liver as a treatment for pernicious anemia. They later suggested a high-protein diet with high amounts of raw liver. This caused a rapid improvement in symptoms and a simultaneous rise in red blood cell counts. Fruit and iron were also part of the diet, and it appears that at this point, Minot and Murphy were not quite sure that the liver was a very important factor. It was thought that iron in liver tissue, not liver juice-soluble factor, cured hemorrhagic anemia in dogs. Thus, the discovery of liver juice as a treatment for pernicious anemia had been by coincidence.