MASQUERADING AS TTP: AN INSIDIOUS PRESENTATION OF B12 DEFICIENCY M Zoya MD, M N Salloum MD Department of Medicine, Louisiana State University, Shreveport, LA INTRODUCTION Pseudothrombotic microangiopathy is a rare presentation of B12 (cobalamin) deficiency. Patients appear ill with elevated reticulocyte count, lactate dehydrogenase (LDH), and total bilirubin with low haptoglobin, platelet count, and anemia - deceivingly suggestive of thrombotic thrombocytopenic purpura (TTP), a type of true and deadly microangiopathic hemolytic anemia. CASE: A 36-year-old female with hypothyroidism presented for anemia with a hemoglobin of 5.1 g/dL and symptoms of fatigue, shortness of breath, palpitations, sweats, chills, vomiting, 54 lb weight loss, easy bruising and tingling in her fingertips and toes for one month. Exam was unremarkable other than pallor. She was found to have an LDH >4,000, haptoglobin <4, platelets as low as 13,000 k/ul, and peripheral smears showing hyper segmented neutrophils and schistocytes. B12 level was normal (295 mg/mL) and methylmalonic acid (MMA) was 1.56 μmol/mmol. Thyroid function panel was near normal. With fear of TTP, she received high dose IV steroids and three days of plasma exchange with minimal improvement in condition. ADAMTS13 is surprisingly found to be negative. Suspicious of B12 deficiency, Hematology recommends daily B12 injections and her symptoms improve. Intrinsic factor (IF) antibody is found to be positive and pernicious anemia is uncovered. DISCUSSION: Malabsorption, not diet, is oftentimes the culprit of B12 deficiency. Most of the absorbed form is done by binding to IF produced by gastric parietal cells, which enhances absorption of B12 in the terminal ileum. Pernicious anemia causes malabsorption via antibodies that impede the B12-IF complex - either targeted at gastric parietal cells or IF itself. In severe cases, it can present with tissue hypoxia symptoms such as shortness of breath in the setting of elevated LDH, reticulocyte count, total bilirubin with low haptoglobin, hemoglobin and platelets. Unlike TTP, the reticulocyte production index (RPI) is <2.0% (reflects inadequate bone marrow response), will not improve with plasmapheresis, MMA will be elevated and median LDH is 3000 (median 1400 in TTP). B12 levels may appear falsely normal in pernicious anemia because of buildup of homocysteine and MMA as a consequence of high levels of IF-Ab, which alters the lab assay.
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