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.