Situs Ambiguus Is Associated With Adverse Clinical Outcomes in Children With Primary Ciliary Dyskinesia

BACKGROUND:Primary ciliary dyskinesia (PCD) is a rare disorder of motile cilia associated with situs abnormalities. At least 12% of patients with PCD have situs ambiguus (SA), including organ laterality defects falling outside normal arrangement [situs solitus (SS)] or mirror image inversion [situs inversus totalis (SIT)]. RESEARCH QUESTION:Do patients with PCD and SA have worse clinical outcomes compared to those with SS or SIT? STUDY DESIGN AND METHODS:This cross-sectional, multicenter study evaluated participants ≤21 years with PCD. Participants were classified as SA, including heterotaxy, or non-SA (SS or SIT). Markers of disease severity were compared between situs groups, adjusting for age at enrollment and severe CCDC39/CCDC40 genotype, using generalized linear models, logistic and Poisson regression. RESULTS:In 397 participants with PCD (mean age 8.4 years, range 0.1-21), 42 were classified as SA, including 16 (38%) with complex cardiovascular malformations (CVM) or atrial isomerism, 13 (31%) with simple CVM, and 13 (31%) without CVM. Of these, 15 (36%) underwent cardiac surgery, 24 (57%) had an anatomic spleen abnormality, and 7 (17%) had both. The remaining 355 participants were non-SA, including 152 with SIT and 203 with SS. Overall, 70 (17%) participants had the severe CCDC39/CCDC40 genotype. Compared to non-SA participants, those with SA had lower median body mass index Z-scores (p=0.03), lower forced vital capacity Z-scores (p=0.01), more hospitalizations and intravenous antibiotic courses for acute respiratory infections during the 5-years before enrollment (p<0.01). Participants with CVM requiring surgery or anatomic spleen abnormalities had lower median body mass index Z-scores and more hospitalizations and intravenous therapies for respiratory illnesses compared to non-SA participants. INTERPRETATION:Children with PCD and SA have worse nutritional and pulmonary outcomes with more hospitalizations for acute respiratory illnesses than those with SS or SIT combined. Poor nutrition and increased hospitalizations for respiratory infections in SA participants with PCD are associated with CVM requiring cardiac surgery and/or splenic anomalies. CLINICALTRIALS:gov: NCT02389049, NCT00323167.