Thoracic involvement in Erdheim-Chester disease: computed tomography imaging findings and their association with the BRAF mutation.

Objectives: To investigate the computed tomography (CT) thoracic findings in Erdheim-Chester disease (ECD) and evaluate the association of these findings with the BRAF mutation.

Methods: This was a prospective study of patients with ECD (n=61, men=46) who underwent thoracic CT imaging. CT examinations were independently interpreted by two experienced radiologists. Association of imaging findings with BRAF was achieved via the Chi-square or Fisher's exact test and odds ratios (OR) with 95% confidence intervals (CI), as appropriate.

Results: Fifty-five ECD patients (90%) showed pulmonary findings, which included interlobular septal thickening (69%), pulmonary nodules (62%), airway thickening (13%) and ground glass opacities (36%). Pulmonary nodules were classified by the pattern of distribution: subpleural regions (36%), lung parenchyma (13%) and both regions (13%). Pleural and mediastinal involvement were present in 15% and 62% of cases, respectively. The most common mediastinal finding was sheathing of the right coronary artery (34%), followed by sheathing of the thoracic aorta (30%). The BRAF mutation, positive in 31 patients, was associated with the frequency of sheathing of the coronary arteries (p = 0.01).

Conclusions: Of the thoracic findings reported in this study, we found a statistically significant positive association between the BRAF mutation and presence of coronary artery sheathing.

Key Points: • To assess the degree of thoracic involvement in ECD with CT. • BRAF mutation has a high association with right coronary artery sheathing. • BRAF genetic testing detects patients at high risk of developing RCA sheathing.