Ciliary Dyskinesia, Primary, 18

A number sign (#) is used with this entry because primary ciliary dyskinesia-18 (CILD18) with or without situs inversus is caused by homozygous mutation in the HEATR2 gene (DNAAF5; 614864) on chromosome 7p22.

For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see 244400.

Description

Primary ciliary dyskinesia-18 is an autosomal recessive disorder characterized by early infantile onset of recurrent sinopulmonary infections due to ciliary dysfunction and impaired airway clearance. Males are infertile and about half of patients have situs inversus. Electron microscopy of cilia shows a defect of the outer and inner dynein arms and impaired ciliary function (summary by Horani et al., 2012).

Clinical Features

Lie et al. (2010) reported 9 Amish patients with primary ciliary dyskinesia. Eight of the 9 had neonatal respiratory distress and all had persistent nasal congestion and coughing. Other clinical findings included chronic rhinosinusitis and pneumonia. Only 1 had recurrent otitis media. Five of the 9 patients had laterality defects. Spirometry showed decreased forced vital capacity, and nasal nitric oxide measurements were extremely low. Ciliary ultrastructural analysis showed absent outer dynein arms.

Horani et al. (2012) provided follow-up of the 9 Amish patients reported by Lie et al. (2010). Affected individuals presented in early infancy with recurrent sinopulmonary infections resulting in progressive respiratory distress. About half of patients had situs inversus, and males were infertile. Electron microscopy showed absent outer dynein arms and most outer doublets lacked inner dynein arms, suggesting a combined defect. Cultured nasal epithelial cells from a patient showed markedly lower levels of HEATR2 compared to controls, and videomicroscopy showed that patient nasal epithelial cells had virtually immotile cilia.

Molecular Genetics

In 9 affected members of an Amish community with primary ciliary dyskinesia-18 with or without situs inversus, Horani et al. (2012) identified a homozygous mutation in the HEATR2 gene (L795P; 614864.0001). The mutation was initially found by exome sequencing of 2 affected children.

Using a targeted exome panel including 26 primary ciliary dyskinesia-associated genes and 284 selected candidate genes in a study of 74 Dutch CILD patients, Paff et al. (2018) identified 2 sibs (PCD-13147 and PCD-3148) with compound heterozygous mutations in the DNAAF5 gene (614864.0002 and 614864.0003). Clinical features of the sibs were not reported.