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Corresponding author at: The University of Texas Health Science Center at Houston, McGovern School of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, Suite 600, 6410 Fannin Street, Houston, TX 77030, USA.
Department of Internal Medicine, The University of Texas Health Sciences Centre at Houston, Houston, TX, USADepartment of Critical Care, Pulmonary and Sleep Medicine, The University of Texas Health Sciences Centre at Houston, Houston, TX, USA
A 64-year-old man with history of chronic anemia and dyspepsia presented with fatigue, exertional chest pain, pedal edema and dyspnea for 2 weeks. His temperature was 37o C, heart rate 74/min, blood pressure was 133/66 mmHg, respiratory rate 18/min, and SpO2 of 96% on ambient air. Laboratory studies showed hemoglobin of 2.73 mmol/L (Normal: 8.56–10.67 mmol/L), mean corpuscular volume (MCV) of 123 fL, platelet count on 32 × 109/L and white blood cell count of 2.8 × 109/L. His indirect bilirubin was 47.9 μmol/L (normal <18 μmol/L), lactate dehydrogenase was 104.7 μkat/L (normal: 1.4–4.1 μkat/L), reticulocyte count was 1.2%, haptoglobin level was <3.65 μmol/L (normal 3.76–25.17 μmol/L) folic acid level was 40.7 nmol/L (normal, >9.1 nmol/L), vitamin B12 was 89.9 pmol/L (normal, >221 pmol/L). Peripheral blood smear (Fig. 1) was concerning for myelophthisic anemia and hence a bone marrow biopsy was performed (Fig. 1b). What is the diagnosis?
The patient has cobalamin deficiency which was found to be secondary to pernicious anemia.
Myelophthisic anemia is due to bone marrow invasion and displacement of immature cells into circulation, by infiltration of abnormal tissue e.g. metastatic cancer, fungal infection, and granulomatous diseases [
]. Hence, finding of nucleated red blood cells (RBC) on peripheral smear is very concerning and usually triggers work-up for ominous causes of myelophthisic anemia. While, cobalamin deficiency is relatively benign and easily managed. Pernicious anemia is caused by intrinsic factor deficiency. It is a protein secreted from parietal cells of gastric mucosa, which binds ingested cobalamin and enables its absorption in distal ileum. Cobalamin deficiency leads to nuclear-cytoplasmic asynchrony resulting in megaloblastic anemia with a hypercellular marrow [
]. Despite the hypercellularity, erythropoiesis is ineffective as the abnormal and fragile RBC precursors' breakdown leading to intramedullary hemolysis, and resultant abnormality of hemolysis labs. While megaloblastic anemia is a universally recognized presentation of cobalamin deficiency, other features like leukoerythroblastosis, hemolytic picture, and splenomegaly are less known [