For a long time, pernicious anemia rightly lived up to its name: it often began with subtle symptoms and was once fatal. Some patients simply appeared exhausted and pale, while others lost their balance or became confused. Large, conspicuous cells were found in the blood; the stomach often exhibited an atrophic, thinned gastric mucosa. Yet the connection remained unclear for a long time.

First raw liver, then concentrated liver extracts, and finally vitamin B12 transformed what had been a near-certain death sentence into a treatable chronic disease. However, while the liver provided the crucial substance, its effectiveness depended on whether the stomach could absorb it.

A Look Inside the Stomach

The story begins with an autopsy. In 1824, the Scottish surgeon James Scarth Combe (1796-1883) reported on a man with severe pallor, diarrhea, and pronounced weakness. Iron supplements, mineral water, and a fortifying diet did not help. The patient died. The autopsy revealed a thin, nearly transparent stomach in which no blood vessels were any longer visible. Today, this would be recognized as a sign of atrophic gastritis.

Thomas Addison (1793-1860) described in 1849 — and in greater detail in 1855 — a severe form of anemia whose cause he could not explain and which, at that time, was almost always fatal. Michael Anton Biermer (1827-1892) defined the condition more precisely in 1871 and named it “progressive pernicious anemia.” It was called “pernicious” because it progressed insidiously and, at the time, had no known effective treatment. Later, the term “Addison-Biermer disease” also became established.

The early findings pointed in two directions. Blood tests revealed unusually large red blood cells; autopsies showed a thin, atrophied gastric mucosa. Yet the crucial question remained unanswered: How could a stomach disease alter the blood so profoundly?

When Anemia Becomes Neurologic

Clinically, pernicious anemia often began harmlessly. Many patients appeared tired, pale, and weakened. But as the disease progressed, it could extend far beyond anemia: the tongue burned, gait became unsteady, and cognitive function changed.

It is precisely this neurologic component that makes the disease relevant today. Blood test results and symptoms do not always correlate. An 89-year-old woman who, after a 2-year interruption in her vitamin B12 therapy, presented with increasing confusion, disorientation, and ataxia.

Hemoglobin and mean corpuscular volume were not especially informative, in part because a vitamin B12 injection given about 30 days earlier, together with concurrent iron deficiency, had confounded the picture. The diagnosis was supported instead by a low vitamin B12 level of 74 pg/mL (normal range, 220-940 pg/mL), a markedly elevated gastrin level of 3942 pg/mL (normal, < 300 pg/mL), and the Schilling test, then the standard assessment of vitamin B12 absorption.

Despite intensive treatment, the patient’s condition showed little improvement; she died on January 7, 1982. The authors’ lesson: Anyone who diagnoses pernicious anemia must initiate lifelong treatment. Anyone who loses sight of this diagnosis risks irreversible neurologic damage.

The Liver Against the Scourge

Even at the beginning of the 20th century, the prognosis was grim. Richard Clarke Cabot (1868-1939) analyzed the clinical courses of 1200 patients in 1907 and found an average survival time of 1-3 years.

Then an organ came into focus that initially seemed to have little to do with the stomach: the liver. George Hoyt Whipple (1878-1976) had observed in animal experiments that liver strongly stimulated blood formation following blood loss.

The hematologists George Richards Minot (1885-1950) and William Parry Murphy (1892-1987) took up this finding. In 1926, they treated patients with pernicious anemia by giving them half a pound of raw beef liver daily. Contemporary reports mention liquid liver, tube feeding, and a specially developed “liver cocktail.” The treatment was labor-intensive, but it worked: patients regained their strength, blood counts improved, and some neurologic symptoms subsided. What had been a near-certain death sentence became a treatable disease. In 1934, Whipple, Minot, and Murphy were awarded the Nobel Prize in Physiology or Medicine for their work on liver therapy.

From Extract to Vitamin

Raw liver saved lives but remained difficult to administer in practice. Edwin Joseph Cohn (1892-1953) produced a liver extract in 1928 that was 50-100 times more concentrated than raw liver. This preparation increasingly replaced the liver diet and was considered the standard therapy well into the 1950s.

The active substance remained unknown at first. It was not until 1948 that two independent research groups identified vitamin B12, cobalamin, as the key anti-anemic factor. This provided a biochemical basis for liver therapy: pounds of liver yielded micrograms of a single vitamin. Dorothy Hodgkin (1910-1994) later elucidated the complex structure of the molecule using x-ray crystallography and demonstrated that it contains cobalt. For this work, she was awarded the Nobel Prize in Chemistry in 1964.

The antianemic factor in the liver had thus been identified. However, it remained unclear why the disease was so closely linked to the stomach. William Bosworth Castle (1897-1990) had already provided a crucial clue in the late 1930s: To absorb the factor later identified as vitamin B12, the body requires intrinsic factor, a glycoprotein produced by parietal cells. It binds to vitamin B12 and enables its absorption in the terminal ileum. If this factor is missing, even a diet rich in B12 is of little use. Atrophic gastritis was thus at the core of the disease and retrospectively explained why liver therapy could be effective at all.

Diagnosis Remains the Sticking Point

In the early 1960s, pernicious anemia came to be recognized as an autoimmune disease. Deborah Doniach, Ivan Roitt, and Keith Taylor demonstrated that antibodies against parietal cells and intrinsic factor are central to the pathogenesis. Pernicious anemia thus does not simply refer to low vitamin levels but rather to an autoimmune disease characterized by a combination of atrophic gastritis, impaired absorption, and megaloblastic blood cell abnormalities. Classic indicators include low B12 levels, elevated methylmalonic acid, and antibodies against intrinsic factor or parietal cells.

Remarkably, Minot and Murphy based their diagnoses entirely on clinical symptoms — a reliable immunoassay for serum vitamin B12 was not developed until 1982. The Schilling test, which assessed B12 absorption, is now considered obsolete and has been replaced by more modern laboratory methods.

A normal complete blood count does not rule out the diagnosis. In cases of neurologic symptoms, glossitis, or fatigue, a vitamin B12 deficiency should be specifically investigated, particularly in older patients. Treatment remains straightforward — vitamin B12, for life in cases of true pernicious anemia. Timely diagnosis is more challenging, especially when neurologic symptoms precede the hematologic signs.

This story was translated from Univadis Germany, part of the Medscape Professional Network.