SHM Converge Scientific Abstract ePoster Gallery-Pernicious Deception: Uncovering Severe Vitamin B12 Deficiency in the Face of Normal Results

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This case describes a 50-year-old man with alcohol use disorder who presented with 3 months of malaise, weight loss, edema, jaundice, macroglossia, ascites, and pleural effusions. His blood smear showed macrocytosis, giant platelets, and hypersegmented neutrophils. Admission labs revealed profound pancytopenia and hemolysis-like findings: hemoglobin 2.3 g/dL, MCV 160 fL, platelets 16,000/mcL, elevated LDH and bilirubin, and low haptoglobin. His serum vitamin B12 level was only borderline low/normal at 243 pg/mL, which could have falsely reassured clinicians.<br /><br />Because severe B12 deficiency was still suspected, methylmalonic acid (MMA) and autoimmune testing were sent, and he was treated empirically with transfusion plus folate, thiamine, and intramuscular cobalamin. After discharge, MMA returned extremely elevated at 263,482 nmol/L, and anti–intrinsic factor and parietal cell antibodies were positive, confirming pernicious anemia due to autoimmune gastritis.<br /><br />The report emphasizes that severe vitamin B12 deficiency can cause megaloblastic anemia and, in extreme cases, hemolysis. Importantly, 30%–50% of patients with pernicious anemia may have falsely normal or elevated serum B12 levels because anti–intrinsic factor antibodies interfere with the assay. Therefore, a normal B12 level does not rule out deficiency.<br /><br />Key takeaways: clinicians should maintain suspicion for B12 deficiency in patients with macrocytic anemia, malabsorption risk, alcohol use, or exposure to PPIs/metformin. If symptoms or smear findings suggest deficiency, MMA should be checked, and patients with severe disease or neurologic symptoms should receive prompt IM cobalamin while confirmatory tests are pending.

Asset Subtitle

Harleen K. Sidhu

Meta Tag

Author List Alberto Busmail Haylock, Aparna Rathnam, Hannah Hugo, Harleen K. Sidhu, Rebecca Ye

Category Clinical Vignettes

Concept Vitamin B12 Deficiency

Concept Vitamin B12 Deficiency Anemia

Concept Serum Vitamin B12 Test

Concept Pernicious Anemia

Concept Methylmalonic Acid

Distinguished Non-Finalist

Presenter Organization Department of Medicine, NYC Health + Hospitals/Elmhurst, Icahn School of Medicine at Mount Sinai

Presenting Author Harleen K. Sidhu

Track Adult

Keywords

vitamin B12 deficiency

pernicious anemia

methylmalonic acid

macrocytic anemia

pancytopenia

hemolysis

autoimmune gastritis

intrinsic factor antibodies

macroglossia

alcohol use disorder

Vitamin B12 Deficiency

Vitamin B12 Deficiency Anemia

Serum Vitamin B12 Test

Pernicious Anemia

Methylmalonic Acid