Differentiation of pernicious anemia from thrombotic thrombocytopenic purpura: The clinical value of subtle pathologic findings.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP) is a microangiopathic hemolytic anemia that requires emergent treatment with plasma exchange and is one of the most important conditions for which apheresis service professionals are consulted. Careful interpretation of initial laboratory values and the peripheral blood smear is a critical first step to determining the need for plasma exchange because other conditions can show deceptively similar red cell morphology, and ADAMTS13 levels are often not rapidly available.

CASE REPORT: We report a case of a patient who was initially diagnosed with TTP and treated with plasma exchange based on preliminary laboratory data and a peripheral blood smear that contained bizarre microcytic red blood cells presumed to be schistocytes. The peripheral blood smear was later interpreted by the hematopathologist to be inconsistent with TTP, and further workup led to a diagnosis of severe vitamin B12 deficiency secondary to pernicious anemia.

RESULTS AND CONCLUSION: This case highlights the diagnostic complexity of thrombotic microangiopathies and the importance of a critical evaluation of the blood smear and presenting laboratory data when there is a concern for TTP.