The grayscale value of positive cells of P-Smad3 (AMPK signaling pathway) in Birt–Hogg–Dubé patients was higher than in patients with simple pulmonary bulla (107.133 ± 1.759 vs. 72.933 ± 6.017, Figures 8(c) and 8(d)). Here, SMAD3 is linked to Pulmonary bulla.