Cancer‐associated microangiopathic hemolytic anemia with thrombocytopenia: an important diagnostic consideration

Background: Early initiation of plasma exchange (PE) allows more than 80% of patients with idiopathic thrombotic thrombocytopenic purpura (TTP), most commonly because of severe ADAMTS13 deficiency, to achieve remission and mandates urgency in diagnosis and therapy. Metastatic cancer may present with a microangiopathic hemolytic anemia with thrombocytopenia that is clinically similar to TTP but does not respond to PE. ADAMTS13 activity can be diagnostic but usually not immediately available. Recognition of cancer‐associated microangiopathic hemolytic anemia with thrombocytopenia (CA‐MHA) is paramount to avoid inappropriate PE therapy and delays in cancer‐specific chemotherapy. Objective: To identify distinguishing characteristics of CA‐MHA and TTP to facilitate early recognition of CA‐MHA. Methods: In a retrospective cohort study, baseline clinical and laboratory data of consecutive adult patients with CA‐MHA (n = 7) or autoimmune TTP (n = 7) from a registry of patients with clinically suspected acute TTP referred for PE were compared. Results: The frequencies of bone pain and respiratory symptoms were significantly greater among patients with CA‐MHA compared to patients with TTP; other baseline clinical and laboratory characteristics did not differ significantly between the two groups. Response to PE and mortality at day 30 were significantly worse for CA‐MHA (14% and 71%, respectively) compared to patients with TTP (86% and 14%, respectively). Conclusions: Baseline clinical and laboratory characteristics largely do not distinguish acute CA‐MHA from autoimmune acute TTP. While all suspected acute patients TTP should receive urgent PE, bone pain, respiratory symptoms, or inadequate PE response should prompt an early search for CA‐MHA.