Primary ciliary dyskinesia with complex abnormalities including cleavage of B-subfibers

Analysis of the clinical features of Japanese patients with primary ciliary dyskinesia

OBJECTIVE

Primary ciliary dyskinesia (PCD) is a rare hereditary disease. Most reports of PCD in Japan are case reports, and clinical analysis has not been performed. Differences in the causative genes might affect the clinical features in different ethnic groups. The purpose of this study was to clarify the clinical features of Japanese patients with PCD.

METHODS

We performed a retrospective chart review of PCD patients seen at Mie University Hospital and patients whose blood samples were sent to us for genetic analysis from 2011 to 2020. Data on the following items were collected and analyzed: age at first visit to the hospital, age at diagnosis of PCD, process of referral to our facility, chief complaint, situs status, PrImary CiliARy DyskinesiA Rule (PICADAR) score, nasal nitric oxide concentration, otoscopic findings, rhinoscopic findings, and paranasal computed tomography scan findings.

RESULTS

Sixty-seven patients (24 male, 43 female) were diagnosed with PCD during the study period. Age at diagnosis ranged from 2 months to 69 years (median, 17 years). Respiratory symptoms (77%) were the most common complaint, followed by nasal (15%) and aural (8%) symptoms. Situs inversus was present in 17 (25%) cases. Only 2 cases had congenital cardiac anomalies. The mean PICADAR score was 7.3 (range, 3-14) points. Approximately 50% of tympanic membranes showed retraction, suggesting otitis media with effusion. The mean Lund-Mackay score was 12.8 (range, 7-17) points, suggesting that the radiographic findings were not always severe. There was no significant difference in the total Lund-Mackay score between patients with and without situs inversus (12.7 vs. 12.6, respectively).

CONCLUSION

Situs inversus was present in 25% of Japanese PCD patients, which is much lower than observed in other countries. This is a result of differences in the major disease-causing genes. The general rule that "situs inversus is observed in approximately 50% of PCD patients" cannot be applied, at least, in Japanese PCD patients.

Primary ciliary dyskinesia with complex abnormalities including cleavage of B-subfibers

A 25‐year‐old Japanese woman suffered from repeated respiratory tract infections. Because of her characteristic medical history and imaging findings, we suspected primary ciliary dyskinesia (PCD) and performed a transbronchial biopsy. The biopsy revealed complex abnormalities of the ciliary structure including cleavage of the B‐subfibers observed by transmission electron microscopy analysis and the complete loss of ciliary motion by video analysis. Genetic examinations to diagnose PCD have progressed in recent years. However, in this case, the well‐known genetic mutations in causal genes of PCD were not detected via whole‐exome sequencing of the blood. Cleavage of the B‐subfibers in patients with PCD has never been reported. This case appears to be the first report of this PCD subtype in humans.