Introduction
Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by
chronic and recurrent sinopulmonary infections due to impaired function
of the motile cilia[1]. The diagnosis of PCD requires a compatible
clinical phenotype accompanied by supportive diagnostic studies. A low
nasal nitric oxide (nNO), <77 nL/min, in a patient with
compatible clinical features, has a high sensitivity
(>98%) and specificity (>99.9%) for
establishing a diagnosis of PCD[1]. However, low nNO levels have
been reported in other disease processes such as cystic fibrosis and
primary immunodeficiencies (PID) [2] and can therefore not solely be
used to make a conclusive diagnosis of PCD. We report two patients with
low nNO values and overlapping clinical symptoms of PCD who were later
determined to have the specific immunodeficiency activated
phosphatidylinositol 3-kinase delta syndrome 1 (APDS1) or PIK3CD.