Physical examination revealed an atrophic, erythematous tongue with loss of the lingual papillae. No deficits were found on neurologic examination.
Laboratory results revealed a hemoglobin level of 13.7 g per deciliter (normal range, 13.1 to 16.6) and a mean corpuscular volume of 101.5 fl (reference range, 83.0 to 95.5).
The serum vitamin B12 level was less than 37 pmol per liter (50 pg per milliliter; reference range, 135 to 675 pmol per liter [180 to 910 pg per milliliter]). The serum folate level was normal.
Test results for anti–intrinsic factor autoantibodies were positive, with a titer of 60 U per millimeter, and the titer for antigastric parietal-cell autoantibodies was 16 U per milliliter (both titers are considered negative at levels of <20 U per milliliter). A diagnosis of pernicious anemia was made.
Treatment with weekly intramuscular injections of vitamin B12 was initiated. The patient’s oral symptoms abated after 2 weeks of treatment, and the atrophic glossitis had resolved by the time of follow-up at 1 month. The patient’s vitamin B12 level increased, and he continues to receive monthly injections.