Can CF also occur without pulmonary symptoms?

Question

Dear Sir/Madam,

My son (3 years and 3 months) is currently being tested for CF. He had a sweat test, but unfortunately the test failed because he didn’t produce enough sweat. However, I do not think my son has CF because he has no pulmonary symptoms. He has upper respiratory infections (with mucus, etc.) but no lung problems. Can it be CF? In other words, are there also CF cases without pulmonary symptoms?

Thank you,
Mother

Answer

Dear Madam,
Thank you for your question.
CF is an inherited disease that mainly affects the lungs, but also other organs such as the pancreas, sometimes the liver and the gallbladder, the upper respiratory airways (especially the sinuses) and also the male reproductive tract. The basic defect (the cause) of this condition is the absence or dysfunction of the CFTR channel, responsible for the transport of chloride, a component of salt, which downstream ensures that the mucus in the lung is sufficiently fluid and not too sticky. You can read about the basic defect of CF in other sections of this website, so we will not further explain that here.
But to answer your question it is important to know that the severity of CF differs from patient to patient. In the most frequent ‘classic forms of CF’ , the CFTR channel is entirely absent or does not work at all. In that case, nearly all patients will have symptoms of poor digestion, poor growth and respiratory problems (such as cough, recurrent infections) from an early age on. In some children the gastrointestinal problems seem more at the forefront than the respiratory problems. The lung problems are however nearly always present, but rather ‘silently’.
There are milder kinds of CF: the chloride channel may have some residual function. This leads to less pronounced symptoms at a young age. In these patients the lungs may not be involved (especially at a young age) and other symptoms may be present: eg repeated inflammation of the pancreas (pancreatitis) or sinusitis at a young age. The diagnosis is often made at a later age compared to the classic form of CF. However, early diagnosis is also important for optimal treatment of these patients.
The best and easiest way to detect CF is the sweat test. Indeed, it can sometimes be unreliable if too little sweat was collected. A second sweat test is then recommended and if this fails again, genetic testing can be done.

As an answer to your question, I can cautiously state that the diagnosis of CF is indeed not ruled out if there is no obvious lung problems.
Of course, this website is intended for general questions, not specific advice. I don’t know why your doctor demanded a sweat test for your son. Therefore, I advise you to go and talk to your doctor for your more detailed questions about your son.


Kind regards
Dr E De Wachter.

08.07.2014