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Primary ciliary dyskinesia
Primary ciliary dyskinesia (PCD) is a rare, genetically heterogeneous, primarily respiratory disorder characterized by chronic upper and lower respiratory tract disease. Approximately half of PCD patients have an organ laterality defect (situs inversus totalis or situs ambiguus/heterotaxy; see these terms).
- Prevalence: -
- Inheritance: Autosomal dominant or Autosomal recessive or X-linked dominant
- Age of onset: Neonatal
- ICD-10: Q34.8
- OMIM: 215518 215520 242670 242680 244400 300991 606763 608644 608646 608647 610852 611884 612274 612444 612518 612649 612650 613193 613807 613808 614017 614679 614874 614935 615067 615294 615444 615451 615481 615482 615500 615504 615505 615872 616037 616481 616726 617091 617092 617577
- UMLS: -
- MeSH: -
- GARD: 4484
- MedDRA: 10069713
PCD has an estimated incidence of 1/15,000-1/30,000 live births, but this is probably an underestimate. Prevalence is difficult to determine.
Affected patients develop signs of PCD at birth or within the first few months of life. Most full-term neonates have respiratory distress with tachypnea (infant acute respiratory distress syndrome) and usually require supplemental oxygen for days, some for weeks. The usual findings in infants and children are daily rhinitis, and daily year-round wet cough occurring soon after birth, with associated recurrent or chronic bacterial infections of the lower airways. Chronic otitis media is common, sometimes with temporary or permanent hearing loss and impaired speech development. Most patients have recurrent sinus infections. Bronchiectasis develops in an age-dependent manner, and is nearly universal in adults. Pectus excavatum and scoliosis have been reported rarely (5-10%), as well as digital clubbing. Almost all males with PCD are infertile, due to dysmotility of spermatozoa, although a few have normal sperm motility. Reduced fertility or a history of ectopic pregnancies has been reported in affected women. Situs inversus totalis, a mirror-image reversal of all visceral organs, is found in 40-50% of individuals and is known as the Kartagener type. Heterotaxy (discordance of right and left patterns of normally asymmetric structures) is present in at least 12%, and a subset of those have structural congenital heart disease. A very rare association of X-linked PCD with either retinitis pigmentosa or intellectual deficiency (see these terms) has been reported.
Pulmonary disease in PCD is related to defects in lung defense mechanisms due to abnormal ciliary structure and function with impaired mucociliary clearance. Mutations in around 30 different genes throughout the genome have been found to be causative. These include DNAH5 15%-21% of cases, CCDC39 2-10%, DNAI1 2%-9%, CCDC40 1-8%, DNAH11 6%, DNAAF1 4-5%, LRRC6 3%, DNAI2 2%, and DNAAF2 <2%. A third of currently recognized patients do not have mutations in these genes.
Diagnosis is based on the characteristic clinical signs and methods include transmission electron microscopy (TEM) identifying specific ciliary ultrastructural defects in biopsy samples and high-speed videomicroscopy to assess cilia waveform and beat frequency. Molecular genetic testing of the causative genes can confirm diagnosis.
The main differential diagnoses are cystic fibrosis (see this term), immunodeficiency syndromes, gastroesophageal reflux, and Wegener's Granulomatosis (see this term).
If disease-causing mutations are known in a family, prenatal diagnosis can be performed.
PCD is inherited in an autosomal recessive manner. Genetic counseling should be provided to affected families. Rare reports mention X-linked or autosomal dominant inheritance.
Management and treatment
Regular clinical visits to monitor disease status are key. Aggressive treatment to improve mucus clearance is recommended. Antibiotic therapy is required and routine immunization is recommended. Sinus disease can be treated with nasal steroids and nasal lavage. Polyps may require surgical treatment. Patients with end-stage lung disease are candidates for lung transplantation. Audiological assessment, hearing aids, and communication assistance should be offered where necessary.
The prognosis depends on timely diagnosis and appropriate treatment. Life expectancy is likely somewhat shortened, although quantitative estimates are not currently available.
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