Introduction

Primary ciliary dyskinesia (PCD) is an inherited genetic disorder diagnosed in childhood, affecting about 1 in 20,000 people. It affects the microscopic structure present in many of the body organs called the cilia.¹ This leads to various symptoms and complications, often evident in early childhood.

Definition and causes

Cilia are microscopic structures in the human body. There are multiple types of cilia, but the most well-known are responsible for motility, or movement.² Other types of cilia involve sensory and receptive roles, for example in vision or neurotransmitting signals in the nervous system.³ They are found in multiple organ systems including respiratory and reproductive systems.²

When cilia malfunction, their functions are impaired. The known role in motility, which is actively involved in clearing pathogens and fluid in areas such as the lungs, ears, and sinuses, can be affected. This reduces the body's effectiveness in clearing infections.¹ Other roles can be affected and lead to impairment of organ development and maintenance.³

PCD is inherited recessively, requiring both asymptomatic parents to carry the gene for the child to be affected.¹ There is a one in four chance of having a child with PCD with every pregnancy. There is a one in two chance of the child being a carrier for the condition with every pregnancy and a one in four chance of the child being neither affected nor a carrier for the gene.⁴

Clinical presentation

PCD presents a spectrum of clinical signs and symptoms. These can vary with age and some occur more commonly than others. This is likely due to the range of cilia structures where some may retain some function, while in other cases, there may be a complete lack of function.⁴

Possible signs and symptoms in children with PCD include:

1. Respiratory symptoms:
   1. Chronic cough
   2. Recurrent respiratory infections
   3. Nasal congestion and rhinorrhoea (runny nose)
2. Ear, nose and throat symptoms:
   1. Otitis media with effusion (acute middle ear infection)
   2. Sinusitis
   3. Chronic middle ear infections
3. Involvement of other systems (rarer):
   1. Situs inversus (where the heart and other organs are found on the opposite side of the body compared to their usual location)²
   2. Congenital heart disease
   3. Male infertility
   4. Hydrocephalus (accumulation of fluid in the brain)
   5. Gastroesophageal reflux

Diagnosis

PCD is not usually a clinical emergency, and investigations can be started in the community. A thorough family history is taken to assess for signs and symptoms.¹ Testing for PCD is often suggested if the child has recurrent chest or ear infections. Testing is only undertaken in specialist centres across the country.⁵

The initial test may be nasal nitric oxide (NO) testing. This is usually only done when the person is above 8 years old as it requires good cooperation with the test. Nasal NO testing requires the person to blow their nose into a machine in a lab setting. If results are abnormal, further testing is conducted.⁴ Pulmonary function tests may also be carried out early on to add to the clinical picture and rule out other possible conditions.⁵

Further testing involves collecting a nasal cell sample using a small brush. These samples are examined under a video microscope to assess cilia function. Genetic testing may also be carried out to identify genes that are known to cause PCD.¹ However, genetic testing may not always pick up the condition, as other genes that are not tested or are not yet known to cause PCD.⁵ Video microscopy of the cell sample remains the gold standard for diagnosing PCD currently.⁴

Management and treatment

Symptomatic management

The majority of acute management options involve relieving symptoms. Antibiotics are usually given to treat active respiratory or ear infections. Those with PCD may also be started on lifelong antibiotic treatment to prevent further infections and progression into lung disease. Other methods of management can also be employed to help facilitate the clearing of particles and fluid from the respiratory system. These include physiotherapy which focuses on the chest to help build strength in clearing mucus and coughing, as well as medications such as mucolytic agents which break down thick fluid and allow it to be better cleared by the body.⁴

Long-term management

Currently, there is no cure for PCD.⁴ Those with PCD are often seen by medical professionals for the rest of their life. Follow-ups are often done annually with members of different teams, including respiratory and ENT doctors, physiotherapists, and nurse specialists.¹ There is advice regarding avoidance of environmental triggers such as tobacco smoke and regular immunisations to help boost general health.⁶

Rarely, lung surgery or transplantation may be indicated if there is severe lung disease. Surgery involving the sinuses and the ears may also be opted for to help prevent recurrent infections and help with symptoms. Looking towards the future, studies into gene therapy have been published, but there are still many hurdles to overcome before they will be able to be applied to clinical settings.⁷

Prognosis and complications

There is a variable prognosis depending on the severity of the disease and active complications. There have only been a few studies done, which are based on relatively few patients. Some may have a benign course, while others may have severely impaired lung function in childhood and rapid disease progression^[6]. Life expectancy is not felt to be altered if treated appropriately, although it may be altered if there are complications such as severe lung disease^[4]. It can have a significant impact on daily life, restricting experiences in school or growing up. However, there are support groups and networks that can help those with PCD as children and as adults. It is important to have discussions and support early on and throughout life to assist the transition and journey through life.⁵

FAQs

What is primary ciliary dyskinesia (PCD)?

Primary ciliary dyskinesia is a condition where microscopic structures called cilia do not function as normal. They are found in the respiratory, reproductive, ear, nose and throat systems. They usually help with cell motility and movement of fluid and particles like bacteria and dust. When they do not function as normal, it can lead to recurrent infections and other health complications.

What causes PCD?

PCD is an inherited genetic disorder, where the cilia do not function because a gene in the body is abnormal. It is autosomal recessive, which means that in two asymptomatic parents, both need to be carriers of the abnormal gene in order for their child to be born with PCD. There is a 1 in 4 chance that parents who are both carriers will have a baby with PCD.

How does PCD affect children?

Most of the clinical symptoms of PCD arise in childhood. This can range from recurrent chest, ear, and sinus infections to abnormal arrangements of the organs of the body (situs inversus). Testing is carried out in children to diagnose PCD and management is started early on to reduce possible complications in the future. Some children may have more severe symptoms and complications than others, which may affect future prognosis as well.

What is the management for PCD?

There is no present cure for PCD. Management usually involves treating active infections and symptoms with antibiotics, physiotherapy and active monitoring by a specialist team. If there are severe symptoms or complications, surgical management may be required. There are support networks available for those with PCD and their families as this is a lifelong condition.

Summary

Primary ciliary dyskinesia (PCD) is an inherited genetic disorder affecting microscopic structures called cilia. It can present with a spectrum of symptoms, some more severe than others. PCD can affect children due to recurrent infections which may cause progressive damage to organs or affect their daily lifestyle in school or growing up. Although there is no cure at present, there is treatment for symptoms of PCD and support given by medical professionals and in the community to help reduce disease progression and impact on lifestyle.