Nasal nitric oxide May not differentiate primary ciliary dyskinesia from certain primary immunodeficiencies.

The diagnosis of primary ciliary dyskinesia (PCD) is made through a combination of clinical features supported by a panel of diagnostic tests. Our cases highlight the similarities in the clinical presentation of patients with the specific immunodeficiency activated phosphatidylinositol 3-kinase delta syndrome 1 (or PIK3CD-related disorder) and PCD. We highlight the importance of repeating nasal nitric oxide testing when PCD has not been confirmed by genetic or ciliary electron micrograph analysis in the setting of an expanded suppurative lung disease differential that includes considerations for immunodeficiency as well as PCD.