Vitamin B12 Deficiency Exhibiting as Pancytopenia: A Diagnostic Conundrum

Pancytopenia is caused by impaired production and peripheral destruction of blood cells, leading to decreased levels of red blood cells (RBCs), white blood cells (WBCs), and platelets. The etiologies can be classified as reversible and irreversible causes. One of the reversible causes is Vitamin B12 deficiency. Vitamin B12 deficiency can cause various types of manifestations, including hematologic as well as neurological symptoms, and sometimes mimicking serious hematologic conditions. A 46-year-old male presented with generalized body weakness, easy fatigability, and occasional nausea with vomiting for two months. His vital signs were stable, and on physical examination, icterus was present. The patient presented with anemia accompanied by leukopenia and thrombocytopenia on complete blood count, suggesting pancytopenia. Red blood cell indices showed macrocytosis, and the peripheral smear revealed teardrop cells along with normocytic normochromic cells, hypersegmented neutrophils, and few macroovalocytes and polychromatophils. Liver function tests showed elevated transaminases and indirect hyperbilirubinemia. A markedly elevated lactate dehydrogenase (LDH) level and low serum Vitamin B12 supported a diagnosis of megaloblastic anemia with associated hemolysis. During the hospital stay, two pints of packed red blood cells were transfused to correct anemia, and considering Vitamin B12 deficiency as the cause of pancytopenia, Vitamin B12 supplementation was started. At the time of discharge, the patient was symptomatically improving and hemodynamically stable. The patient was prescribed ursodeoxycholic acid, thiamine, and Vitamin B12 supplement. On follow-up, the patient was symptomatically better, and improvement was observed in lab findings as well. In brief, this case study showcases the vague clinical presentation of Vitamin B12 deficiency, making its diagnosis challenging. Therefore, Vitamin B12 deficiency should be considered as an important differential in cases with pancytopenia, which aids in its prompt treatment and eliminates unnecessary procedures.