Atypical cystic fibrosis is a milder form of cystic fibrosis (CF), a degenerative condition that parents pass to their children. Atypical CF symptoms tend to be milder, and people may not know they have the condition until adulthood.

CF is a condition that affects the lungs, the digestive system, and other organs. It causes a person’s body to produce sticky, thick mucus or sweat that can obstruct or damage tubular organs. It is a result of a mutation in the cystic fibrosis transmembrane receptor gene (CFTR) gene.

Atypical CF can cause fluctuating symptoms that are typically less severe than those of typical CF. The organs that atypical CF affects can also vary from person to person.

This article discusses the symptoms and causes of atypical CF. It also looks at treatment options, diagnosis, and more.

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A person with atypical CF may experience respiratory symptoms that are milder than those of typical CF. These can include:

CF is a genetic condition. As with typical CF, scientists believe that atypical CF results from mutations in the CFTR gene.

People with atypical CF will usually have one severe CF mutation on one of their chromosomes and one less common, mild CF mutation on the corresponding chromosome.

They may also have an abnormal number of trinucleotide repeats in the CFTR gene on one chromosome and one severe mutation on the other.

Because the symptoms of atypical CF are very similar to those of typical CF but milder, treatments for atypical CF are generally the same as those for typical CF.

Treatments can include:

Close follow-ups with a doctor specializing in CF treatment can help identify any complications early and allow for appropriate treatments to help extend the life expectancy of a person with atypical CF.

Atypical CF can be difficult to diagnose because the symptoms can be mild, varied, and slow to progress.

If a doctor suspects atypical CF, they can order various tests that may help them reach an accurate diagnosis.

Sweat chloride testing

Sweat chloride testing is now the standard test to diagnose CF in adults. It can also help diagnose atypical CF in cases where a person has elevated chloride levels.

To perform this test, a healthcare professional will apply an odorless, colorless chemical and a small amount of electrical stimulation to a person’s leg or arm to detect levels of chloride in their sweat. A hospital lab will then test the sweat to analyze the chloride levels.

Genetic testing

Genetic testing can help confirm the diagnosis if the CFTR gene mutation is present.

For this test, a person must provide a sample of their blood, skin cells, or saliva.

Doctors have been diagnosing atypical CF since the 1960s. However, because doctors may identify many of its symptoms as other conditions, atypical CF can be hard to diagnose, and many doctors may initially misdiagnose it as another condition or group of conditions.

For this reason, although there is no specific age at which people are most likely to receive a diagnosis of atypical CF, people usually receive a diagnosis in adulthood or older adulthood.

One 2020 case report describes a person who received a diagnosis of CF at age 57 years despite having numerous symptoms since childhood. Another 2020 case report details a person who experienced numerous CF symptoms and received a diagnosis of atypical CF at age 30 years. In this second case, doctors were able to diagnose CF through sweat chloride testing.

Because CF can be hard to diagnose, people living with it may not receive the treatment they need and may be more likely to die from the condition. If a person thinks they may have symptoms of atypical CF, they should consult a doctor promptly so they can receive an accurate diagnosis as early as possible.

About 1,000 people receive a CF diagnosis each year, and around 10% of all CF diagnoses occur in adulthood.

Here are some more frequently asked questions about atypical CF.

What is the life expectancy for a mild case of cystic fibrosis?

Due to the difficulties in diagnosing atypical CF, experts have had trouble finding a specific answer to this question.

While adults who receive a diagnosis of atypical CF generally have longer life expectancies than those with typical CF, experts still do not know the long-term outcome for many people with atypical CF.

Starting treatment as early as possible may help reduce symptoms and improve quality of life.

Can you have mild cystic fibrosis and not know it?

It is very possible to have mild CF or atypical CF without realizing it because healthcare professionals may mistakenly attribute the symptoms to a related condition.

For this reason, a person should contact a doctor if they suspect they may have CF or if they have experienced symptoms or conditions such as:

  • chronic, unrelenting sinus congestion and recurrent sinus infections
  • chronic cough with sticky mucus
  • recurrent episodes of pneumonia
  • severe abdominal pain
  • chronic diarrhea or constipation
  • delayed puberty or fertility problems
  • unintentionally low weight or body mass index

Atypical CF is a milder form of CF. Symptoms can vary from person to person and can lead to misdiagnosis because they are similar to those of other conditions.

A person with atypical CF may not realize they have the condition until later in life. People typically receive the diagnosis in adulthood.

A sweat chloride test or genetic testing can help healthcare professionals diagnose atypical CF. Receiving an accurate diagnosis and starting treatment as early as possible can help a person manage symptoms and experience the best possible outlook for the condition.