This case report was published in the New England Journal of Medicine.
Noting the patient’s confusion and aphasia, emergency medical services were alerted, and she was taken to the emergency department of Massachusetts General Hospital. Initial examination revealed aphasia and coordination difficulties. However, imaging studies, including CT angiography, showed no signs of stroke or other neurological abnormalities.
The patient’s coworkers had observed that she appeared “unwell.” Her medical history included hypertension, which was managed with amlodipine, and there was no known family history of neurologic disorders.
During the examination, her vital signs were within normal ranges.
The patient’s potassium level of 2.5 mmol/L was noteworthy, indicating hypokalemia. Additionally, the patient presented with anemia and thrombocytopenia. Additional laboratory results unveiled thrombotic thrombocytopenic purpura (TTP), a rare blood disorder characterized by microangiopathic hemolytic anemia. The microscopic examination of a peripheral blood smear confirmed the extent of thrombocytopenia and was particularly notable for the increased number of schistocytes. The patient’s peripheral blood smear revealed five or six schistocytes per high-power field, constituting approximately 5% of the red cells. This significant number of schistocytes aligned with the severity of anemia and thrombocytopenia, confirming the diagnosis of microangiopathic hemolytic anemia.
Acquired TTP is an autoimmune condition driven by antibody-mediated clearance of the plasma enzyme ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motif 13). Confirmatory laboratory testing for ADAMTS13 takes 1-3 days; therefore, therapeutic plasma exchange with glucocorticoid therapy and rituximab was initiated, which promptly improved her condition.
In this patient, the ADAMTS13 activity level was severely reduced (< 5%; reference value > 67%), and the inhibitor was present (1.4 inhibitor units; reference value ≤ 0.4).
Rectal cancer was diagnosed in this patient 2 months after the diagnosis of acquired TTP.
After undergoing four weekly infusions of rituximab and a 2-month tapering course of glucocorticoids, the patient experienced a relapse, approximately 6 months following the acquired TTP diagnosis. In response, therapeutic plasma exchange and glucocorticoid therapy were administered. There is a possibility that the underlying cancer played a role in the relapse. To minimize the risk for recurrence, the patient also received a second round of rituximab.
While establishing a clear cause is difficult, acquired TTP often appears to arise in connection with either an immune trigger, such as a viral infection, or immune dysregulation associated with another autoimmune disease or ongoing cancer. In this case, 4 weeks before the acquired TTP diagnosis, the patient had experienced COVID-19, which was likely to be the most probable trigger. However, rectal cancer was also identified in the patient, and whether these conditions are directly linked remains unclear.
A version of this article first appeared on Medscape.com.