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Pernicious Anemia With Spuriously Normal B12 Levels
Ana Isabel Brochado1, Joana Marques Dias1, Marta Azevedo Ferreira1
1Internal Medicine Department, Hospital Beatriz Ângelo, Loures, PRT.
Cureus
|December 18, 2023
Summary
Pernicious anemia can cause severe macrocytic anemia and hemolysis, even with normal vitamin B12 levels. Intrinsic factor antibodies can interfere with B12 testing, leading to misdiagnosis.
Area of Science:
- Hematology
- Gastroenterology
- Immunology
Background:
- Pernicious anemia is an autoimmune condition affecting the stomach lining.
- It leads to vitamin B12 deficiency and megaloblastic anemia.
- Diagnosis can be challenging due to potential assay interferences.
Observation:
- A 29-year-old man presented with fatigue, palpitations, and hemolysis.
- Pancytopenia with macrocytic anemia and hemolysis was noted.
- Initial vitamin B12 and folate levels appeared normal.
Findings:
- Bone marrow biopsy suggested megaloblastic anemia.
- Atrophic gastritis was observed on upper endoscopy.
- Elevated homocysteine and positive intrinsic factor antibodies confirmed pernicious anemia.
- Vitamin B12 levels were spuriously normal due to intrinsic factor antibodies.
Implications:
- Intrinsic factor antibodies can interfere with standard vitamin B12 assays.
- Accurate diagnosis of pernicious anemia requires considering antibody testing.
- Prompt replacement therapy leads to rapid clinical recovery.
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