Morphometric Study of Pulmonary Arterial Changes in Pulmonary Langerhans Cell Histiocytosis

- Pulmonary hypertension (PHT) is a complication of pulmonary Langerhans cell histiocytosis (PLCH); however, the pathogenesis remains largely unknown. Few studies have evaluated histopathologic changes in pulmonary arteries (PAs) of patients with PLCH; systematic quantification of arterial remodeling has yet to be undertaken.

- To quantify the extent of arterial remodeling among patients with PLCH through morphometry and to correlate these results with pertinent clinical parameters.

- Patients with PLCH were identified from institutional files (1995-2015) along with age-, sex-, and smoking status-matched controls. Morphometric analysis of intimal and medial thickness of small to medium PAs was performed in patients with PLCH (within PLCH lesions [lesional] and away from PLCH lesions [nonlesional]) and controls. Paired measures were compared with Wilcoxon signed rank tests.

- Twenty-five patients with PLCH (14 men: median age, 46 years; interquartile range, 37-55 years) and 25 controls were included. The lesional arteries of patients with PLCH demonstrated thicker PA intima and media than controls ( P < .001 and P < .001, respectively), as did PLCH nonlesional arteries compared to controls ( P < .001 and P < .001, respectively). The PA intima and media were thicker within the PLCH lesions than nonlesional arteries ( P = .02 and P = .002, respectively). Patients with PLCH-related PHT had a worse prognosis than those without PHT ( P = .04; hazard ratio, 4.5 [1.1, 22.2]). Echocardiography parameters including right atrial size ( P = .007), estimated right atrial pressure ( P = .01), and right ventricular systolic pressure ( P = .01) were inversely associated with survival.

- Our findings suggest that factors other than direct vascular obstruction or inflammatory cell infiltration contribute, at least in part, to the vascular remodeling in PLCH.