Pulmonary tumour thrombotic microangiopathy (PTTM) is a rapidly progressive pulmonary disease that is a fatal complication of malignancy. It manifests clinically as subacute respiratory failure with pulmonary hypertension, progressive right sided heart failure, and sudden death. We describe here a case of PTTM associated with occult metastatic signet ring cell carcinoma of the stomach. Although rare, PTTM needs to be considered in the differential diagnosis of dyspnoea of unknown origin, particularly in patients with respiratory failure and also pulmonary hypertension, and in patients were there is no improvement in respiratory symptoms with steroid therapy.