What is Cystic fibrosis?
Cystic fibrosis (CF) is a hereditary disease, caused by a defective gene. It is a form of recessive inheritance, which means that both parents are carriers of the defective gene. The symptoms of the disease are varied and are attributed to the production of thick viscid mucous. This can result in damage to several organs and can give rise to intestinal obstruction, failure to thrive and recurrent infections of the lungs.
Ireland currently has the highest proportion of people with CF in the world. An estimated 900 people here have the condition.
While 30 or 40 years ago a baby born with CF was unlikely to live beyond early childhood, now with advances in research and treatment, the majority of people with it survive well into their adult years.
What are a person’s chances of inheriting CF?
Around one in 20 people are carriers of the CF gene. Where two carriers of the gene parent a child together, there is a one in four chance that the baby will be born with CF. There is a one in two chance that the child will be a carrier of the gene, just like its parents, and there is a one in four chance that the child will neither inherit the disease nor be a carrier of the gene. The relevant gene is known as CFTR (cystic fibrosis transmembrane regulator) gene. It is now possible to identify the presence of this gene with a blood test. Over nine hundred mutations of this gene have been identified, each of which can cause CF.
What are the symptoms of CF?
Symptoms of CF usually appear within the first year of life. However in some rare cases, they may not appear until adolescence or even adulthood.
The pattern of symptoms and signs is very variable and could include some of the following:
- Chronic or recurrent respiratory symptoms, such as a cough or a wheeze.
- Recurrent or chronic pneumonia.
- Malformed, bulky, offensive stools, with an oily appearance.
- Chronic diarrhoea.
- Prolonged jaundice.
- Rectal prolapse, which means that a small portion of the rectum can protrude through the anal orifice.
- Failure to thrive.
- Some parents notice that the child tastes salty when kissed.
- Dehydration in hot weather, more susceptible to heat stroke.
While most children will have displayed symptoms within their first year, some will show symptoms later, at the pre-school age.
Sometimes, when dealing with children with recurrent chest infections there may already be evidence of extensive lung damage at the time of diagnosis.
If the diagnosis is made at a more advanced stage of the disease the following symptoms and signs might be present:
- Persistent cough, with or without sputum.
- Unexplained chronic or recurrent wheezing.
- Rectal prolapse.
- Chronic diarrhoea.
- Unexplained liver disease.
- Clubbing of the fingers.
- Salt crystal formation on the skin.
- Slow weight and height gain.
Most cases of CF will have been diagnosed by the time the child starts school. Those who are diagnosed after that time tend to have a milder form of the disease but may show signs of malnutrition. They may also have abnormal stools and recurrent respiratory symptoms.
How is CF diagnosed?
If CF is suspected, the diagnosis can be confirmed through a special sweat test. The sweat test has been internationally recognised for the past forty years as the ‘gold standard’ test for the diagnosis of CF. If the test is positive it is usually repeated in order to confirm the diagnosis. Given the implications of a positive sweat test one positive result is not regarded as being sufficient.
How is a sweat test performed?
The sweat test is a painless procedure that does not involve the use of needles. A special pad is placed on the child’s lower arm or leg. This pad is soaked with pilocarpine, which is a chemical that induces sweating in the underlying skin. The pad is secured in place and a painless electrical current is passed through the pad for several minutes. This induces a mild tingling sensation in the skin. The pad is then removed and the skin is washed with pure water and carefully dried. A piece of blotting paper is then applied to the skin and is held in place with an adhesive strip and the area is covered with cling film. Over the course of the following half hour the blotting paper absorbs sweat from the child’s skin. The piece of blotting paper is then removed and sent to the laboratory where the level of salt in the sweat is measured.
How is CF treated?
Children with two positive sweat tests are usually referred to a special CF clinic. Hospitals in Ireland with such clinics include:
- St Vincent’s Hospital, Dublin (adults only).
- Our Lady’s Hospital for Sick Children in Crumlin, Dublin (children only).
- Cork University Hospital (both adults and children).
- Limerick Regional Hospital (both adults and children).
- Waterford Regional Hospital (both adults and children).
- University College Hospital Galway (both adults and children).
In the case of Limerick, Waterford and Galway, these hospitals are linked to St Vincent’s in Dublin. Therefore ongoing care, support and follow up is organised through the local hospital in conjunction with St Vincent’s.
Treatment aims to maximise lung function. Asthma among CF sufferers is common, so asthma inhalers may be used. Antibiotics are also used frequently because of the damaging effects of recurrent infection on the structure of the lungs.
Complications involving the pancreas can be managed by controlling the patient’s diet and adding supplements of pancreatic enzymes to food.
If lung function deteriorates very significantly, a heart and lung transplant may be required.
There are some exciting possibilities being investigated at present with regard to gene therapy but such treatments are for the moment experimental and are not generally available.