COL4A5 and Buschke-Ollendorff syndrome: This stratification showed an inverse correlation between serum concentration of COL4A5, predicted FVC (Fig. 3a) (r = − 0.56 p = 0.03), and FEV1 (Fig. 3b) (r = − 0.42 p = 0.04) at the time of diagnosis of BOS and reached particular statistical significance for patients who died.