Respiratory failure in a cancer patient: pulmonary thrombotic microangiopathy.

The hypoxic patient with a normal chest X-ray can be a diagnostic challenge. This case illustrates the rational diagnostic process and describes a relatively rare but important complication of cancer metastasis. Thrombotic microangiopathy, like lymphangitis carcinomatosa, may cause respiratory failure and is a poor prognostic finding. However, unlike lymphangitis carcinomatosa, it may not have specific findings on cross-sectional imaging.