Disseminated Malignancy Misdiagnosed as Thrombotic Thrombocytopenic Purpura: A Report of 10 Patients and a Systematic Review of Published Cases.

Patients with disseminated malignancy who present with microangiopathic hemolytic anemia and thrombocytopenia may be misdiagnosed as thrombotic thrombocytopenic purpura (TTP), resulting in inappropriate plasma exchange treatment, a procedure with major risk, and delay of appropriate chemotherapy. We report the 17 year experience of The Oklahoma TTP-HUS Registry, 1989–2005, and a systematic review of previously published case reports. Ten of 335 consecutive patients in the Oklahoma Registry who were initially diagnosed with their first episode TTP and treated with plasma exchange were subsequently discovered to have disseminated malignancy; only one had a history of cancer. These 10 patients were compared to the 133 concurrent patients with idiopathic TTP.

Patients with disseminated malignancy had a longer duration of symptoms, were more often men, had more frequent presence of respiratory symptoms, higher LDH levels, more often failed to respond to plasma exchange treatment, and had a higher mortality. Neurologic abnormalities, hematocrit, platelet count, and serum creatinine were not different between the two groups. Diagnosis of malignancy was made by bone marrow biopsy in 6 patients but not until autopsy in 2 patients. A systematic review identified 19 additional patients, reported from 1965 to 2005, in whom TTP or HUS was initially suspected and systemic malignancy subsequently discovered. Only 5 patients had a history of cancer. Malignancy was not diagnosed until autopsy in 6 patients. Fourteen different malignant disorders were diagnosed in these 29 patients.

CONCLUSIONS: Disseminated malignancy may be occult and may mimic TTP. A search for systemic malignancy, including a bone marrow biopsy, is appropriate when patients diagnosed with TTP have atypical clinical features or fail to respond to plasma exchange.