CCNO mutation as a cause of primary ciliary dyskinesia: A case report

Case Report: Primary ciliary dyskinesia due to CCNO mutations: a Chinese pediatric case series and literature review

Primary ciliary dyskinesia (PCD) is a hereditary disorder characterized by defects in cilia that impair mucociliary clearance. This study focuses on PCD caused by mutations in the Cyclin O (CCNO) gene and reports on three cases involving Chinese children. Case 1 was an 8-year-and-3-month-old boy who presented with respiratory distress after birth and later developed a recurrent productive cough and purulent nasal discharge. He was initially diagnosed with diffuse panbronchiolitis (DPB) due to the presence of diffuse micronodules in lung CT scans. Case 2 was the younger sister of case 1. She also presented with respiratory distress after birth, with a chest radiograph revealing atelectasis. She required oxygen supplementation until the age of 2 months. Case 3 was a 4-year-and-4-month-old girl with a history of neonatal pneumonia, persistent pulmonary atelectasis, and recurrent lower respiratory tract infections. Her chest radiograph also showed diffuse micronodules. In all three cases, the final diagnosis of PCD was confirmed by genetic testing. Cases 1 and 2 exhibited homozygous c.248_252dup TGCCC (p.G85Cfs*11) mutations in the CCNO gene, while case 3 harbored a homozygous c.258_262dup GGCCC (p.Q88Rfs*8) mutation. A literature review indicated that the common clinical features of CCNO-PCD include neonatal respiratory distress (40/49, 81.6%), chronic cough (31/33, 93.9%), rhinosinusitis (30/35, 85.7%), bronchiectasis (26/35, 74.3%), and low nasal nitric oxide (nNO, 40/43, 93.0%). Notably, situs inversus has not been reported. In CCNO-PCD patients, cilia may appear structurally normal but were severely reduced in number or entirely absent. Lung CT scans in these patients may exhibit diffuse micronodules and "tree-in-bud" signs, which can lead to a clinical misdiagnosis of DPB. nNO screening combined with genetic testing is an optimized diagnostic strategy. Treatment options include the use of anti-infective and anti-inflammatory agent, along with daily airway clearance. This study underscores the importance of genetic testing in neonates and children with suspected PCD or those clinically diagnosed with DPB to enable an early diagnosis and prompt intervention, thereby enhancing the prognosis for these patients.

Two Japanese Pediatric Patients With Primary Ciliary Dyskinesia Caused by Loss-of-Function Variants in the CCNO gene

Primary ciliary dyskinesia (PCD) is a rare congenital disorder caused by pathogenic variants of genes related to cilia. Here, we report two Japanese pediatric patients with PCD caused by pathogenic compound heterozygous variants in the cyclin O (CCNO) gene (Case 1, NM_021147.4:c.[262C>T];[781delC], p.[Gln88Ter];[Leu261fs]; Case 2, c.[262C>T];[c.248_252dupTGCCC], p.[Gln88Ter];[Gly85fs]). The clinical symptoms of the patients were varied. Neither of the patients had situs inversus. Transmission electron microscopy of the respiratory cilia from the nasal mucosa in Case 1 showed a remarkable reduction of cilia and the few residual cilia had central pair defects and microtubular disorganization.

The First Case of a Homozygous CCNO NM 021147.4 Mutation Associated With Primary Ciliary Dyskinesia in Two Indian Siblings

Primary ciliary dyskinesia (PCD) is a heterogeneous autosomal recessive disease marked by organ lateralization in 50% of patients, chronic sinopulmonary disease, infertility in men, and neonatal respiratory distress. Respiratory control cells contain CCNO in their apical cytoplasm, which is necessary for the development of multiciliate cells, basal body amplification, and migration. Reduced generation of multiple motile cilia, a rare form of PCD, has been linked to CCNO gene abnormalities. Individuals with CCNO mutations have been reported to suffer from severe lower respiratory infections that cause progressive impairment of lung function. For the first time, we describe the CCNO NM 021147.4 (c.258 262dup.p, Gln88argfs*8 Homozygous) gene mutation in an Indian consanguineous family that resulted in severe PCD.