Background: YNS is an orphan disease, the prevalence is estimated to be <1/100000. The typical clinical sign is the triad of yellowish discoloured nails, lymphedema and respiratory manifestations. The pathogenesis is still controversial. It may be observed in the context of malignancy, autoimmune diseases and rarely be hereditary. The treatment is symptomatic and clincial trials are not available.

Objective: To describe the phenotype of patients with YNS and bronchiectasis to identify targets for future research regarding the pathogenesis, diagnosis and specific treatment. Methods:  Data from the German and European bronchiectasis registries PROGNOSIS and EMBARC was analyzed descriptively. Differences between subjects with YNS (pooled data from PROGNOSIS and EMBARC) and other etiologies of bronchiectasis (data from PROGNOSIS) were assessed by Fisher´s exact, Chi2 and Mann-Whitney-U test.

Results: Overall, 31 patients in PROGNOSIS and EMBARC had YNS as aetiology. Median age was 67 yrs; 58% were female, the median (IQR) FEV1% predicted was 68% (59-83) and 32% grew Pseudomonas aeruginosa in sputum cultures. Bronchiectasis were seen predominantly in lower lobes.Compared to 994 subjects without YNS from PROGNOSIS registry significant differences were observed with regard to the proportion with chronic rhinosinusitis (CRS) (52% in YNS vs. 30%; p=0.016) and the median [IQR] exacerbation frequency (2 [1-6] vs. 1 [0-3]; p=0.009).

Conclusion: Our data suggest that YNS is a rare cause of bronchiectasis, which may be associated with frequent exacerbations and rhinosinusitis. Further multicenter research is warranted.