Trends in pulmonary function in patients with Birt-Hogg-Dubé syndrome: A retrospective cohort study

<bold>Background</bold> Birt-Hogg-Dubé syndrome (BHD) is a rare genetic disease characterized by multiple pulmonary cysts that can lead to spontaneous pneumothorax, cutaneous hamartomas, renal cysts and renal cell cancer. The overall aim of this study was to assess clinical characteristics of patients with BHD- emphasizing on trends in pulmonary function patterns. <bold>Methods</bold> By use of data from electronic patient journals, we conducted a retrospective cohort study on clinical characteristics and pulmonary function tests (PFT) from patients with BHD, who were clinically followed-up in a Danish tertiary referral center for rare and interstitial lung diseases. <bold>Results</bold> A total of 101 patients (44 men (43.6%); mean age 48.4 years (standard deviation (SD) ±15.9 years)) with BHD were included. Chest high-resolution computed tomography scans revealed pulmonary cysts in 82.2% of whom 38.6% had experienced at least one pneumothorax (median 2; interquartile range 1-4). Baseline PFT showed FEV1/FVC ratio and RV% within normal values of predicted. In 28.7% of the patients, a slight decrease in DLco below 80% of predicted was observed (mean 86.9% ± SD 15.8%). At two years follow-up, there were no significant declines in FEV1 and FVC, nor after accounting for age, gender, and smoking. At baseline cutaneous manifestations were found in 58.4% of the patients, 47.5% had benign renal cysts, and 11.9% had renal tumours. <bold>Conclusion</bold> More than 80% of patients with BHD presented with pulmonary cysts, but consistent with other studies all had normal PFTs at two years follow-up. We conclude that routine monitoring of pulmonary function and pulmonary follow-up may not be necessary in patients with BHD.