Pernicious Anemia Presenting as a Mimicker of Thrombotic Thrombocytopenic Purpura.

A 52-year-old woman with no significant past medical history presented to the emergency room (ER) with nonspecific systemic symptoms, including fatigue, dyspnea on exertion, easy bruising, and palpitations. She was found to have significant pancytopenia. Hemolytic anemia, thrombocytopenia, and elevated PLASMIC score (6, High risk; PLASMIC = Platelet count; combined hemoLysis variable; absence of Active cancer; absence of Stem-cell or solid-organ transplant; MCV; INR; Creatinine) score at the time of presentation led to a concern for thrombotic thrombocytopenic purpura (TTP). Therapeutic plasma exchange (TPE) was deferred pending additional investigation. Workup revealed the true diagnosis of severe B12 deficiency, which would not have benefited from TPE and instead would have placed the patient at risk for harm, making the decision to defer treatment the correct and judicious approach. This is a case where anchoring on lab results may result in reaching the incorrect diagnosis. This case reminds clinicians of the importance of creating a broad differential and ensuring thorough history-taking is done for all patients.