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Dear experts,

I would like to know more about atypical forms of cystic fibrosis and tests, especially forms with involvement of the digestive system and the pankreas.
Are there forms of Mukoviszidose without an involvement of the lung or at least a very late involvement of the lung within the process of the illness?

I read about infections with pseudomonas which do occur very often with this illness;
is a long lasting infection with pseudomonas in a toe an indicator for cystic fibrosis?

Many thanks in advance.
Thank you for your questions.
1) Cystic fibrosis (CF) is a disease caused by a genetic mutation which results in the abnormal production and function of a gene called the cystic fibrosis transmembrane conductance regulator (CFTR). This gene controls the movement of chloride ions in and out of cells.

In most patients with CF, the diagnosis is confirmed by a positive sweat test (that is, the amount of chloride ions in the sweat is measured). In CF this is usually high (greater than 60mmol/l). In addition the diagnosis is confirmed by 2 mutations on the CFTR genes. In this classical CF, symptoms such as lung disease and abnormalities in the digestive system may also be present.

Patients with non-classic or atypical CF may have either a normal ((less than 30mmol/l) or borderline (30 to 60mmol/l) sweat test result. A diagnosis of atypical CF requires the detection of 2 mutations on the CFTR genes or confirmed abnormal functioning of the CFTR on a sweat test or by a test known as nasal potential difference measurement. In the latter test, a small device is inserted up the nose which measures the difference in chloride ion levels between the inside and outside of the cell. This indicates if the CFTR is working properly or not.

There are over 1500 different types of mutations of the CFTR gene. Patients with atypical CF tend to have rare mutations and milder disease. A couple of research studies have looked at adults with inflammation of the pancreas (a symptom found in some adults with CF). They found that a proportion had atypical CF, although rarely did any have lung disease.

In addition to those with atypical CF, there are some patients with classic CF who also have mutations which are associated with milder disease and may only develop symptoms later in life.

2) Pseudomonas infection in a toe is not an indicator for CF. It is more likely to be an indicator of diabetic or vascular disease in the foot.

We hope this is useful for you,

Best wishes,

Stuart Elborn

Judy Bradley

Lauren Wilson
The answer is edited by: Prof Stuart Elborn