Primary Ciliary dyskinesia (PCD) is defined as a medical condition affecting the movement of the cilia. But what are cilia, what happens when they don't move properly (dyskinesia) and how does it affect the body?

What Are Cilia?

Unless you have PCD you may not even be aware that your body is full of cilia, but cilia are actually pretty vital pieces of equipment. The PCD Support Group website defines cilia as '...the microscopic hairs which beat in the airways to sweep secretions out of the respiratory tract'. In a healthy respiratory system, where the cilia do their job, mucus is swept to the larger airways where it can be disposed of, usually by coughing. It could be said that the cilia are the protectors of the respiratory system. They may be small, but they're very important.

What Happens to the Cilia in Someone With PCD?

The cilia of people with PCD may be deformed, causing them not to move properly, or they may not have developed at all. However, they may also appear to be normal, but still not function correctly.

What Happens If the Cilia Don't Move Properly?

People with PCD are prone to infections of the lungs (chest infections), sinus infections (sinusitis) and ear infections. They may seem have a perpetually runny or blocked nose. This is because the mucus that should be swept away by the cilia just sits in the airways. This can cause infection, and, once infected, it is difficult for a person with PCD to get rid of infection. In cases of chest infection, for example, infected mucus is not cleared away by the cilia but remains in the lungs, prolonging the period of infection. Because of the frequency of infection to organs such as the lungs and ears, long-lasting or permanent damage may result. Hearing loss is common among people with PCD.

The effects of severe PCD are similar to those of Cystic Fibrosis (CF), and are sometimes mistaken for this disease. A 'sweat test' can determine whether a person has PCD or CF. Unlike CF patients, people with PCD will have normal sweat chloride values. The PCD Foundation website describes the medical history of a 'typical PCD patient' thus:

...includes neonatal respiratory distress (coughing, gagging, choking, lung collapse as a newborn), chronic cough, pneumonia, bronchitis, atelectasis [collapsed lung or lungs failing to fully expand at birth], excess mucus and difficulty clearing lung secretions. Otitis media (middle ear infections) and hearing loss are universal in this patient population, as are severe sinus infections.

As well as the respiratory system and abdominal organs, other areas of the body can be affected. Cilia are also found in the ventricles of the brain, so people with PCD may experience severe headaches. The reproductive system of both men and women with the condition may also be affected: The tail of the sperm is similar in structure to that of cilia, so any problems with movement of the cilia may also be present in the sperm, making their journey to fertilise the egg more difficult. In women, infertility may occur because the fallopian tubes are lined with cilia to aid the journey of the egg; if the cilia are ineffective this may hinder the progress of the egg and damage or reduce a woman's chances of a successful conception.

About half the people who have PCD also have a condition called situs inversus totalis. Situs inversus totalis (SIT) means the abdominal organs, including the heart, liver, spleen and intestines, are in mirror-image positions to their normal location in the abdominal cavity. These organs may still work properly even though they are in a reverse position, but problems with the heart, liver and spleen have been reported in people with SIT. Where PCD and situs inversus totalis occur together the condition is known as Kartagener's Syndrome.

The symptoms of people with PCD vary according to the severity of the person's condition. People who have relatively mild cases can live a fairly normal life, and will only need physiotherapy if they suffer a particularly severe chest infection. Others require physiotherapy twice a day as a matter of course, and even more often if they contract an infection.

What Causes PCD?

Not much is known about PCD, but it is thought to be a recessively inherited condition – both parents must carry the defective gene. It currently affects about one in 15,000 people, so it is relatively rare.

Treatment

The most important treatment for PCD is physiotherapy to clear the airways and try to prevent infection.

In the past, people with PCD who suffered from chest infections had to be tipped over a pile of cushions and 'clapped' on the side to loosen the mucus, after which they coughed it out into a plastic pot. It was not very enjoyable, as you can imagine. Thankfully, since those days better physiotherapy techniques have been developed. There are breathing routines that can help, and these are much more practical and convenient, particularly for people who are not at home.

In case of infection, antibiotics are required immediately, as mucus in the airways is breeding ground for diseases. In case of particularly severe infections, admission to hospital and the use of intravenous antibiotics may be necessary. Bronchodilators, mucolytics (mucus thinners) and steroids are also used to treat the effects of PCD.

Psycho-social Affects of PCD

As mentioned above, many people with PCD need to do physiotherapy several times a day to clear mucus from the lungs to try to decrease the risk of chest infections. Obviously, it's not very convenient to require physiotherapy twice a day if you're at work or school, or even just out for the day. Recurrent chest and/or ear infections and sinusitis may also mean that the person with PCD has to take a large amount of time off from work or school. Dr Chris McManus of University College London has done, and is continuing to do, research into the psycho-social effects of PCD.