Atypical cystic fibrosis

What is so-called atypical cystic fibrosis?

In its typical form, cystic fibrosis (CF) is diagnosed in children in the first years of life: repeated digestive complications or bronchopulmonary infections may raise suspicion. In recent decades, the development of certain diagnostic tests such as the measurement of the difference in nasal potential and the complete analysis of the CFTR gene have allowed the identification of less severe forms of CF and the diagnosis of the disease in adulthood. The process of diagnosing these atypical forms of the disease is sometimes complex because the CFTR function is often less disturbed and the diagnostic tests sometimes discordant.

Atypical cystic fibrosis is therefore a less intense form of classical cystic fibrosis. People living with atypical CF usually combine a severe mutation with a less common mutation. Instead of having the usual symptoms, these people may have a dysfunction in a single organ system that is much less severe than those with two severe mutations. They may or may not have high levels of chloride in their sweat. As a result, these individuals often require less hospitalization during childhood than those with classical CF and the problem may remain undiagnosed for many years, sometimes even into adulthood. In some cases, there have even been diagnoses in people aged 70. Over time, people with atypical CF may develop other symptoms or discover that pre-existing health conditions are CF symptoms that were not previously identified as such. It is estimated that 10% of CF cases could be described as atypical.

In fact, a book was written on the subject a few years ago. Now That I Have CF: Information for Men and Women Diagnosed as Adults, (available only in English), this publication is specifically aimed at people diagnosed in adulthood and suffering from a so-called atypical form of the disease.

Note that thanks to neonatal screening, which is now carried out on all newborns in Quebec, the discovery of late cases of CF should be increasingly rare in the future.

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