Cystic fibrosis symptoms mostly involve the lungs, digestion, and (in some people) fertility, and they usually start in childhood but can also appear later in life.

What is cystic fibrosis in simple terms?

Cystic fibrosis (CF) is a genetic condition where the body makes very thick and sticky mucus instead of thin, slippery mucus. This mucus can block small tubes in the lungs, pancreas, and other organs, leading to breathing problems, trouble digesting food, and frequent infections.

Think of it like pipes in a house getting clogged with sludge: air, digestive juices, and other fluids can’t move properly, so everything backs up and causes problems.

Common lung (respiratory) symptoms

These are often the most obvious and tend to show up early.

  • Persistent cough that doesn’t go away, often bringing up thick mucus (phlegm).
  • Wheezing or a squeaky sound when breathing.
  • Shortness of breath or getting tired quickly with exercise or activity.
  • Frequent chest or lung infections, such as pneumonia or bronchitis.
  • Frequent sinus infections, sinus pain, or a blocked, stuffy nose; sometimes nasal polyps (small growths in the nose).

These symptoms happen because the thick mucus blocks airways and traps bacteria, making infections and inflammation more likely.

Digestive and gut symptoms

CF often affects how well the body digests and absorbs food.

  • Large, greasy, foul‑smelling stools that may be hard to flush away.
  • Oily or loose stool, or stool that floats or contains mucus.
  • Constipation, sometimes severe, with belly pain, bloating, or a swollen‑looking stomach.
  • Blocked intestines (especially in newborns), sometimes leading to vomiting and severe belly pain.
  • Poor appetite at times, nausea, and reflux (heartburn or food coming back up).

Because digestive enzymes can’t reach the intestine properly, the body can’t fully use fats and nutrients, which leads to poor weight gain and vitamin deficiencies.

Growth, weight, and general body symptoms

CF can affect overall growth, energy, and how someone feels day to day.

  • Poor weight gain or trouble gaining weight even with a good appetite and enough calories.
  • In children, not growing as quickly or as tall as expected; in teens, delayed puberty.
  • Tiredness, low energy, or reduced ability to exercise.
  • Very salty‑tasting skin or “salty” sweat; sometimes salt crystals visible on the skin after sweating.
  • Muscle cramps or weakness in hot weather because of extra salt loss in sweat.
  • Swollen, rounded fingertips and nails (“clubbing”) in some people with long‑term lung disease.

Parents sometimes first notice CF because their baby or child is not gaining weight, has frequent greasy stools, and keeps getting chest infections.

Other symptoms (pancreas, liver, fertility)

CF is a whole‑body condition, so it can affect several organs beyond lungs and gut.

  • Repeated inflammation of the pancreas (pancreatitis), which can cause upper belly pain, nausea, and vomiting in some older children and adults.
  • CF‑related diabetes, a form of diabetes caused by pancreatic damage.
  • Liver problems and gallbladder issues in some people, sometimes leading to jaundice or abnormal liver tests.
  • Male infertility due to blocked or missing sperm ducts; many men with CF cannot father children without medical help.
  • In some adults, milder or “atypical” CF may show mainly as chronic sinus problems, recurrent pancreatitis, or unexplained infertility, rather than classic childhood symptoms.

These problems appear because the same thick secretions that clog airways can also block ducts in the pancreas, liver, and reproductive system.

Do symptoms change with age?

Yes, symptoms can look different in babies, children, and adults.

  • Newborns: delayed passing of the first stool (meconium ileus), swollen belly, vomiting, or bowel blockage.
  • Babies and young children: chronic cough, frequent chest infections, poor weight gain, greasy stools, and slow growth.
  • Teens and adults: ongoing cough and lung infections, sinus problems, digestive issues, low weight, fatigue, fertility issues, and sometimes CF‑related diabetes or pancreatitis.

Because newborn screening is common in many countries now, more people are diagnosed earlier, sometimes before obvious symptoms appear.

When to seek medical help

Because CF is serious but treatable, it’s important not to ignore patterns of symptoms.

You should contact a doctor or pediatrician promptly if you notice:

  • A cough that lasts for weeks, especially with thick mucus or repeated chest infections.
  • Poor growth or weight gain in a child despite good feeding, or greasy, very smelly stools.
  • Very salty‑tasting skin, frequent sinus or lung infections, or clubbing of the fingertips.
  • Unexplained male infertility or recurring pancreatitis in an adult, especially if there’s any family history of CF.

Doctors may order a sweat test (to measure salt in sweat) and/or genetic testing to confirm or rule out CF.

Quick HTML table of key cystic fibrosis symptoms

html

<table>
  <thead>
    <tr>
      <th>System</th>
      <th>Common symptoms</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Lungs & sinuses</td>
      <td>Persistent cough with thick mucus; wheeze; shortness of breath; frequent chest infections; recurrent sinus infections; nasal polyps.[web:3][web:7][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Digestive system</td>
      <td>Large greasy or foul-smelling stools; constipation; belly pain and bloating; intestinal blockage (especially in newborns); poor appetite at times.[web:3][web:7][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Growth & nutrition</td>
      <td>Poor weight gain; slow growth in children; delayed puberty in teens; fatigue; reduced exercise tolerance.[web:3][web:7][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Body and skin</td>
      <td>Very salty sweat or skin; possible salt crystals on skin after sweating; muscle cramps or weakness in heat; clubbed fingertips in longstanding disease.[web:5][web:7][web:1][web:8]</td>
    </tr>
    <tr>
      <td>Pancreas & metabolism</td>
      <td>Pancreatitis (recurrent belly pain); CF-related diabetes; vitamin deficiencies from poor absorption.[web:1][web:3][web:6][web:8]</td>
    </tr>
    <tr>
      <td>Reproductive system</td>
      <td>Male infertility due to blocked sperm ducts; in atypical CF, infertility may be a main feature.[web:1][web:5][web:6][web:8]</td>
    </tr>
  </tbody>
</table>

Quick note and disclaimer

If you or someone you know has symptoms that sound like cystic fibrosis, especially long‑lasting cough with thick mucus plus trouble gaining weight, it is important to see a healthcare professional for proper testing and diagnosis. Early diagnosis and modern treatments have greatly improved outcomes and life expectancy for people living with CF.

Information gathered from public forums or data available on the internet and portrayed here.