Lung function in Birt-Hogg-Dubé syndrome

Abstract

Introduction: Birt-Hogg-Dube syndrome (BHDS) is a rare inherited autosomal dominant disorder characterized by cutaneous fibrofolliculomas, renal tumors, multiple pulmonary cysts and spontaneous pneumothoraces. BHDS is caused by mutations in the tumor suppressor gene FLCN coding for folliculin. Only limited data on lung function in BHDS are available, and whether lung function declines over time as in other cystic lung diseases is unknown. Aims: To assess lung function at baseline and over time in BHDS. Methods: We retrospectively studied lung function parameters from 30 patients with BHDS at baseline and during disease course, and looked for correlations with age, gender and smoking history. Results: Mean±SD age at baseline was 42±14 yr, 60% were males, 43% were smokers and 90% had pulmonary cysts at HRCT. Baseline FEV1 and FVC (n=30) were 95±13 and 100±14 %pred respectively, and FEV1/FVC ratio was 80±6%. TLC (n=21) was 98±15 %pred, RV (n=21) was 111±30 %pred, DLCO (n=18) was 86±16 %pred, KCO (n=19) was 96±20 %pred, and PaO2 (n=8) was 88±11 mmHg. FEV1, FVC and FEV1/FVC at 1, 2 and 3 years follow-up (n= 12, 9 and 6 respectively) were not significantly different from baseline. FEV1/FVC tended to decrease with age at baseline (p=0.05) and over time (p=0.02). In smokers, FEV1 was 9% lower at baseline (p=0.08) and over time (p=0.013) as compared to non-smokers. FVC significantly increased with age at baseline (p=0.007) and over time (p=0.002). Other parameters at baseline and over time were not correlated with age, gender and smoking history. Conclusions: These data suggest that cystic lung disease in BHDS does not affect respiratory function at baseline, and that no deterioration occurs over a follow-up period of 3 years.