Pulmonary capillary hemangiomatosis associated with connective tissue disease: a report of 4 cases and review of the literature.

Pulmonary hypertension (PHTN) can be seen in patients with connective tissue disease (CTD). The typical pathology associated with CTD is interstitial fibrosis and hypertensive pulmonary arteriopathy. We describe 4 patients with CTD and PHTN unexpectedly found to have pulmonary capillary hemangiomatosis (PCH) at explant after lung transplantation or autopsy. Pulmonary capillary hemangiomatosis is defined as a proliferation of capillaries in alveolar walls and can clinically cause PHTN. We detail the pathologic findings of PCH, describe the differential diagnosis, and present a review of the literature on the possible association of PCH with CTD. Although PCH may present clinically as PHTN, it is critical to differentiate between the typical CTD-associated interstitial fibrosis with hypertensive pulmonary arteriopathy and PCH because the treatment is different. We provide the largest case series to date and highlight the need for pathologists to have a high level of suspicion for PCH in patients with CTD.