Pernicious anaemia: diagnosis should be certain before treatment is begun.

Patients with pernicious anaemia have a megaloblastic anaemia or a neuropathy due to cobalamin deficiency resulting from malabsorption of cobalamin due to gastric atrophy. To diagnose pernicious anaemia all the elements of the definition must be satisfied.

About one in 100 people over 60 have pernicious anaemia, and for every person with the condition there are another 10 generally healthy people who never develop the clinical features of pernicious anaemia despite histamine fast achlorhydria, gastric atrophy, and sometimes a low serum concentration and impaired absorption of cobalamin. Diagnosis must distinguish between these two groups.

Changes in the peripheral blood in the least anaemic patients with pernicious anaemia are macrocytosis and some anisocytosis; in more anaemic patients there is also poikilocytosis and hypersegmented neutrophils. The bone marrow shows megaloblastic haemopoiesis. Rarely neuropathy may be present in the absence of blood changes. Macrocytosis may be absent in patients who have small red blood cells …