Background: Primary ciliary dyskinesia (PCD) due to CCNO mutations is frequently associated with more severe clinical phenotypes. This study reports our experience with three patients and reviews global characteristics of CCNO-related cases, providing insights for early diagnosis. Methods: We conducted a retrospective analysis of PCD patients with CCNO mutations and reviewed genotype-phenotype correlations in the literature. Results: Three pediatric cases of PCD with CCNO mutations were enrolled in our department. All patients were born with respiratory distress and exhibited recurrent wet cough, wheezing, or dyspnea. Bronchial mucosal biopsies from all patients revealed the absence of ciliary structures. Patients exhibited nasal nitric oxide (nNO) levels below the normal range. All three patients had sinusitis; Patient 1 also suffered from otitis media, mastoiditis and hearing loss. Head magnetic resonance imaging (MRI) revealed arachnoid cyst in patient 1 and ventricular enlargement in patient 3. Patient 2 carried a novel homozygous point mutation in exon 3 (c.884T>C/homo; p.L295P), and echocardiography revealed moderate pulmonary hypertension. Our literature review indicated that neonatal onset respiratory symptoms were the major manifestations. Low nNO levels were observed in 89.2% of patients. Heterotaxy was absent in all cases. Bronchiectasis was the most common radiological finding. A total of 20 mutations were identified in 55 patients. Conclusion: Neonatal respiratory distress and reduced nNO levels are common clinical features of CCNO-related PCD.Genetic testing is essential for the early diagnosis of CCNO-related PCD.

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Background: Primary ciliary dyskinesia (PCD) is a rare genomic disorder. The phenotype heterogeneity depends on the genotype. Critical genes mutant like CCNO had severe respiratory disease, while limited data are available until now. Case presentation: We presented a patient with neonatal respiratory distress at birth, and had cough with wheeze for 8 years as flows. According to clinical and imaging findings, screenings of PCD related genes showed compound heterozygous mutation of CCNO. We also overviewed the literature of CCNO-related PCD and compared to our patient. A total of 43 patients from 30 families were enrolled. Approximately 57.1% (24/42) of individuals were born in the consanguineous marriage family. Most patients developed onset symptoms at neonate, accounted for 85.3%. Recurrent respiratory tract infection (83.3%), neonatal respiratory distress (69.0%), and sinusitis/rhinorrhea (50.0%) were major manifestations, the subsequents were chronic cough 15/42(35.7%), and recurrent otitis media (28.6%); hear losing, infertility, congenital heart defects and hydrocephalus were rare, but heterotaxy was never seen. Bronchiectasis was the most common radiologic findings, while the patient in our study presented with special findings of diffuses small nodular in both lungs like diffuse pan-bronchiolitis (DPB). Thirteen different CCNO variants were identified with most located in exon 1 (79.1%, 34/43). Our participant was identified previously reported c.263_267dupAGCCC and c.258_262dupGGCCC mutation from her mother and father respectively. Conclusion: CCNO variants are rare in PCD patients, but it causes more severe phenotypes than the other genes. Neonatal respiratory distress is common, and diffuse bronchiolitis could be the radiologic feature of CCNO-related PCD.