Introduction
Primary Ciliary Dyskinesia (PCD) is a rare condition, often diagnosed in infancy or early childhood. The term PCD may be used interchangeably with Kartagner’s syndrome and presents with a classical triad and a separate clinical finding. The symptoms sometimes overlap with features of another important major condition- cystic fibrosis- but the underlying disease mechanisms and investigation findings are different. This article will explore the causes and symptoms that are associated with PCD.
Epidemiology
Kartagner’s syndrome is a subdivision of primary ciliary dyskinesia. According to the National Organisation for Rare Disorders, PCD affects around 1 in 20,000 births.1 The incidence of Kartagner’s syndrome is approximately 1 in 32,000 to 40,000 births, and thus it is very rare. It is noted that around 50% of people with primary ciliary dyskinesia have Kartagner’s syndrome, which is why the two terms are so closely linked and often used interchangeably.2 Current data does not provide much information on whether gender is associated with an increased incidence of PCD. However, PCD is more likely to be found in communities that commonly engage in consanguineous marriages, i.e. the parents of the affected child are blood relatives.
Causes of Primary Ciliary Dyskinesia
PCD results in defective cilia. Cilia are microscopic hair-like structures lining several parts of our body to allow for the movement of mucous, fluids, and other substances. For example, the cilia lining the respiratory tract can help to clear the airways of any secretions. In PCD, patients have abnormal motility of cilia, with or without abnormal ciliary morphology.3 The condition is referred to as “autosomal recessive”. This means that a child would need to have two recessive copies of a gene (alleles) to have the condition. For this reason, consanguinity increases the risk of acquiring PCD - the child can have two copies of the same genetic mutation that might be commonly carried in a certain family. This does not mean that the parents are affected by PCD. Individuals can carry abnormal genes, without having any conditions, unless they have two copies of an abnormal gene. There are over 50 genes that, if faulty, can cause PCD.
What are the symptoms of Primary Ciliary Dyskinesia?
Cilia have a major role in the respiratory tract. So when their function is affected, it leads to abnormal and reduced clearing of mucus and bacteria. Therefore, PCD will cause recurrent infections of the lungs, ears, and nose. Symptoms related to sinusitis, rhinitis, chest infections, and glue ear can be present too. However, these conditions are common in childhood even in children unaffected by PCD. The distinguishing factor is that they are chronic and may not respond to treatment.4 Children may show poor growth (and in severe cases, failure to thrive), as well as bronchiectasis, which results from recurring chest infections that can cause irreversible damage to the lungs, particularly the bronchi. As the bronchi become scarred and dilated, their function is reduced and mucus can easily pool in them, leading to further respiratory issues and breathing difficulty.
So, what exactly is Kartagner’s syndrome? Kartagner’s syndrome is a combination of PCD as well as situs inversus,5 an even rarer syndrome where a person’s internal organs are all mirrored inside the body. This means that the heart sits on the right side of the chest instead of the left and that the liver lies on the left side of the body instead of the right side. The internal organs are not defective or abnormal, however, which is why situs inversus in itself does not typically cause medical problems. Congenital heart diseases may be associated with situs inversus, in which case affected individuals may exhibit signs and symptoms resulting from those defects.
A common term you may come across with regards to PCD and Kartagner’s syndrome is Kartagner’s triad. It describes the three key features of PCD, and are therefore hallmarks for suspecting the disease:
- Paranasal sinusitis
- Bronchiectasis
- Situs inversus
Note that not all patients will have all three of these features (e.g. situs inversus only affects about 50% of individuals with PCD), but they are very common nonetheless.
Another possible symptom (or rather complication) of PCD is infertility/subfertility. For males, the movement of the sperm will be impacted, so male patients are often infertile. In females, there may be infertility as the cilia in the fallopian tubes are affected. Subfertility is also possible, and female patients are at increased risk of having ectopic pregnancies.
Summary
Primary Ciliary Dyskinesia or Kartagner’s syndrome, describe the reduced or absent motility of cilia, which means that substances, such as mucus, can not be cleared or moved easily. It is an autosomal recessive disease and can present with recurrent respiratory infections, poor growth and subfertility.
References
- Primary ciliary dyskinesia - symptoms, causes, treatment | nord [Internet]. [cited 2024 Apr 10]. Available from: https://rarediseases.org/rare-diseases/primary-ciliary-dyskinesia/
- Wahba M. Radiopaedia. [cited 2024 Apr 10]. Kartagener syndrome | radiology reference article | radiopaedia. Org. Available from: https://radiopaedia.org/articles/kartagener-syndrome-1?lang=gb
- What is primary ciliary dyskinesia (Pcd)? | Asthma + Lung UK [Internet]. 2022 [cited 2024 Apr 10]. Available from: https://www.asthmaandlung.org.uk/conditions/primary-ciliary-dyskinesia-pcd/what-is-it
- Kartagener’s syndrome: causes and treatment | doctor [Internet]. 2022 [cited 2024 Apr 10]. Available from: https://patient.info/doctor/kartageners-syndrome
- Cambridge University Hospitals [Internet]. [cited 2024 Apr 10]. Kartagener’s syndrome. Available from: https://www.cuh.nhs.uk/patient-information/kartageners-syndrome/