Ciliary Dyskinesia, Primary, 9

A number sign (#) is used with this entry because primary ciliary dyskinesia-9 (CILD9) can be caused by homozygous mutation in the DNAI2 gene (605483) on chromosome 17q25.

For a general description and a discussion of genetic heterogeneity of primary ciliary dyskinesia and Kartagener syndrome, see CILD1 (244400).

Description

Primary ciliary dyskinesia is an autosomal recessive disorder resulting from loss of normal ciliary function. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus, and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003).

Clinical Features

Loges et al. (2008) reported a consanguineous Iranian Jewish kindred in which 2 individuals had primary ciliary dyskinesia characterized by neonatal pneumonia, recurrent rhinitis and sinusitis, recurrent otitis media and hearing deficits, chronic cough, and bronchiectasis. Two additional family members had these features and situs inversus, consistent with Kartagener syndrome. One affected male had infertility. Electron microscopic studies showed defects of the outer dynein arm in the axonemes of respiratory cilia and sperm tails.

Knowles et al. (2013) reported 3 unrelated individuals of Ashkenazi Jewish descent with CILD9. The patients had neonatal respiratory distress, sinusitis, otitis, bronchiectasis, and decreased nasal nitric oxide; 2 had situs inversus. Respiratory epithelial cells showed ciliary outer dynein arm defects.

Molecular Genetics

In affected members of 3 unrelated families with CILD9, Loges et al. (2008) identified 3 different homozygous mutations in the DNAI2 gene (605483.0001-605483.0003). Affected cilia showed a complete loss of functional DNAI2 protein, consistent with recessive loss-of-function mutations.

In 3 individuals of Ashkenazi Jewish descent with CILD9, Knowles et al. (2013) identified a homozygous truncating mutation in the DNAI2 gene (W453X; 605483.0004). The mutation was identified by exome sequencing; haplotype analysis indicated a founder effect.