Objective: The purposes of this study were to identify diagnostic imaging markers for differentiating pulmonary cysts in lymphangioleiomyomatosis and Birt-Hogg-Dubé syndrome and to identify potential risk factors for spontaneous pneumothorax in the two diseases.
Materials and methods: This retrospective study included 44 patients with lymphangioleiomyomatosis (44 women; mean age, 35 ± 10.9 years) and 13 patients with Birt-Hogg-Dubé syndrome (nine men, four women; mean age, 45.1 ± 10.9 years). CT findings were analyzed to determine the shape; presence of septation, wall visibility, and subpleural cysts; size; number; distribution; location of the largest cyst; and presence of cysts encircling the bronchovascular bundle ("air-cuff" sign) and of mediastinal fat indentation. Multiple logistic regression was performed to identify risk factors for spontaneous pneumothorax.
Results: Compared with patients with lymphangioleiomyomatosis, patients with Birt-Hogg-Dubé syndrome were significantly older, and more of them were men. The cysts in these patients had a more irregular shape, more septation, lower and more peripheral distribution, larger maximum size, and more attachment to the pleura, air-cuff sign, indentation on mediastinal fat, and subpleural cysts larger than 2 cm. The maximum diameter of cysts was the sole independent risk factor for spontaneous pneumothorax (p = 0.027; 95% CI, 1.043-1.992) in both diseases. ROC analysis showed an AUC of 0.745 (95% CI, 0.612-0.851), and the optimal cutoff value was 22 mm (sensitivity, 72.5%; specificity, 76.5%).
Conclusion: Several CT imaging markers may help in differentiating pulmonary cysts in patients with lymphangioleiomyomatosis and those with Birt-Hogg-Dubé syndrome and in predicting spontaneous pneumothorax.
Keywords: Birt-Hogg-Dubé syndrome; CT; lymphangioleiomyomatosis; pulmonary cyst.