To further understand the impact of WFDC2 deficiency, we analyzed saliva from healthy control individuals (n = 3), individuals with WFDC2 mutations (n = 3), and control individuals with respiratory disease (PCD, n = 2; CF, n = 2) by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Here, WFDC2 is linked to primary ciliary dyskinesia.