Pulmonary Tumor Thrombotic Microangiopathy with Administration of Pulmonary Vasodilator Resulting in Clinical Improvement Prior to Final Diagnosis

BACKGROUND The pathophysiology of pulmonary tumor thrombotic microangiopathy (PTTM) was recently revealed by autopsy. Considered rare, we suggest that this fatal disease is not rare, but has not been diagnosed pre-mortem. Some patients with pulmonary thromboembolism with unknown thrombus source or with sudden death have been treated for malignant carcinoma. We report a patient with PTTM who was successfully rescued acutely by treatment with soluble guanylate cyclase (sGC), resulting in appropriate palliative care. CASE REPORT An 80-year-old Japanese woman was transferred to our emergency room for severe dyspnea owing to type I respiratory failure. Her clinical findings indicated pulmonary thromboembolism, but we found no thrombus in either the pulmonary artery or inferior vena cava. However, we incidentally found gallbladder cancer with peritoneal metastases. These findings raised the suspicion of PTTM. We began concurrent sGC and direct oral anticoagulant (DOAC) on the assumption that PTTM had occurred, while performing peripheral pulmonary artery sampling for cytology, and pulmonary perfusion scintigraphy. Cytology revealed several aplastic cells; consequently, we finally diagnosed PTTM. Because she did not wish to undergo examination and active treatment for carcinoma, we initiated palliative care while continuing sGC. She was able to spend time with her family for more than 100 days, without dyspnea. CONCLUSIONS We must recognize PTTM, which is a lesser-known disease, and introduce diagnostic therapy with a pulmonary vasodilator, such as sGC, immediately, when we suspect PTTM, leading to appropriate clinical care.