30 May 2007

Cystic fibrosis: are you a carrier?

Lisa and Paul were ecstatic to hear they were going to be parents. What they didn't know was that they both carried a gene that put their baby at risk for a dangerous disease.

When Lisa and Paul heard that they were going to have a baby, they were ecstatic. After all, they had been trying for a year and Lisa was pushing 37. Nothing was going to dampen their enthusiasm.

But what the couple didn't know at the time was that they both carried a gene that predisposed their unborn child to a dangerous disease.

Neither of them had any symptoms that could have warned them. The defective gene merely slumbered in their separate family lines through many generations.

So, when their paediatrician made the "cystic fibrosis" diagnosis, the couple didn't know what it meant. All they knew was that their six-month-old boy had a chronic cough and frequent lung infections – sometimes to the extent that he had difficulty breathing – and that he wasn't picking up weight.

Many carry the gene
Lisa and Paul's story echoes thousands of others throughout the world. Even though modern treatment methods have made a marked difference in terms of life expectancy, cystic fibrosis (CF) is still a serious, life-shortening disease.

What's more, many of us unknowingly carry the gene.

If you're a healthy white South African, there's a 1 in 27 chance that you are walking around with one copy of a gene mutation that causes CF. If you should, by chance, meet a partner who also carries a CF gene mutation, there is a very real danger that one of your children could be affected.

Each pregnancy between two carriers results in a 1 in 4 chance of having a child with this condition and a 1 in 2 chance of having a child who will be a carrier of the disease. The disease can go undetected for generations. "In most families we deal with, there is no family history of CF," says Dr Tony Westwood, general paediatrician at the Red Cross War Memorial Children's Hospital in Cape Town.

CF affects the cells
The cells of people who have CF differ from healthy cells. Sodium and chloride are not moved in and out of the cells as they should be. This leads to excessive mucus production by the cells that line the lungs, intestine, sweat glands, pancreas, liver and reproductive tract.

The thick mucus can block any of the ducts in these organs. For example, it has the potential to fill the lungs, triggering lung infections, and can prevent the body from properly absorbing food. It may also lead to liver damage.

Symptoms of CF include chronic cough, salty skin, difficulty breathing, bulky offensive-smelling stools and poor weight gain, despite a significant appetite.

Infection and inflammation of the airways and progressive lung destruction is, in most cases, the cause of death.

Disease does not discriminate
Although the disease has traditionally been considered a disease of European origin and is more common among the white (1 in 3000 births) and, to a lesser extent, the coloured (1 in 10 000 births) population groups in South Africa, it is now also increasingly being recognised among the black population.

But, while the identification of new cases among black children has accelerated in recent years, their numbers are still very low compared to the numbers expected, according to Westwood and Prof Michele Ramsay from the National Health Laboratory Service and the University of the Witwatersrand.

At this stage, there are only about 500 people known to have CF in South Africa. It has been suggested that the "missing" CF children are dying in early infancy, labelled as having tuberculosis, malnutrition or even HIV/Aids.

This is a pity, especially considering the fact that early detection and intensive treatment make it possible for people with CF to live well into adulthood.

According to Westwood, many South Africans who have the condition live to the age of 40 and beyond. But death in childhood still occurs sometimes.

Should you get tested?
If you and your partner are planning a pregnancy, it could be worth your while to get a genetic test done – especially if the two of you are distantly related, and fall into the white or coloured population group.

"Among the white population, we can test for potential carriage and pick up 91% of carriers," Westwood says. "But there is still the possibility that the genetic mutations will not be identified."

Unfortunately, it's not so easy to pick up the mutations in the coloured and black population groups as there is less certainty about the mutations involved. However, limited testing can still be done.

The tests cost approximately R1 780 per person for white and coloured couples and approximately R830 for black couples.

Early diagnosis important
According to Westwood, early diagnosis and intensive treatment are crucial.

If your child doesn't grow normally, has a persistent cough and/or has recurrent chest problems – even if the symptoms are mild – you should get the child tested.

As these symptoms may also point to asthma, it's important to get a proper diagnosis.

At the moment, there is still no cure for the disease. Some breakthroughs are being made in terms of novel treatments but it will be many years before they become available.

"It's all about controlling the consequences," Westwood says. "As CF is a very complex disease, several experts need to be involved in the management of the disease."

To locate a dedicated CF clinic close to you, contact the South African Cystic Fibrosis Association on (021) 557 0323 or (011) 294 3849.

(Carine van Rooyen, Health24, May 2007)




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