Cystic fibrosis
Definition
An autosomal recessive inherited illness. It basically makes all the exocrine glands screw up, thus causing problems in the lungs, liver, pancreas and intestines.
Epidemiology
In white Europeans its about 1 in 2,500 births. For some reason, the less that description matches you, the rarer CF is. So in black Africans, its 1 in 10,000, and native Asians, more like 1 in 25,000.
Pathophysiology
Its complex. Simple version; the ion transporters in the exocrine cells don't work properly. This means the excretions end up super concentrated, becoming thick and gooey. As you might suspect, this might have some impact on various body organs:
- The lungs fill with goo - this makes them much better at picking up infections, and much less good at getting rid of them. Many CF sufferers end up with a chronic Pseudomonas infection, and frequently get pneumonia.
- The pancreas fills with goo - this blocks it up, and prevents enzymes from passing into the digestive tract, leading to malnutrition. It also blocks insulin passing through, and the built up enzymes attack the Islets of Langerhans, causing diabetes and pancreatitis.
- The liver fills with goo - the jury is out on exactly what this does, but liver failure is the second highest cause of death in CF sufferers. They often develop cirrhosis, and that's bad.
- The intestines fill with goo - and this can present as meconium ileus, where the first batch of a baby's poo gets stuck in the ileum as it mixes with the extra mucus. In 20% of CF sufferers, they will diagnosed soon after birth due to this happening.
- Infertility is very common - women get filled with goo which screws up the ovaries, and 97% of men get a congenital absense of the vas deferens
Risk Factors
Since this is an inherited condition, the only risk is family history, and specifically; if both of your parents are carriers of the CFTR gene, then you will get it. Parents can thus screen themselves before pregnancy to see if there is a risk for their children.
Clinical Features
Lungs
- Recurrent respiratory infections, especially pneumonia
- Persistent cough, with lots of goo (sputum)
- Wheezing, shortness of breath, and other non specific symptoms
Gastrointestinal
- No stools in the first 1-2 days of life (see meconium ileus, above)
- Pale, floating or smelly stools
Systemic
- Salty tasting skin
- Failure to thrive
- Clubbing
Investigations
For diagnostics, they use the sweat test - as it comes from an exocrine gland, the sweat is mega concentrated in sodium, chlorine and other ions, and this shows up in testing.
There is also the IRT test - Immunoreactive Trypsinogen. This is done on neonates, and is used to screen. Basically, if its high they are more likely to have CF, so you do another test...
Management
- Antibiotics - Chest infections are a big problem. To deal with it, many CF sufferers are on long term antibiotics, increasing them when they get an infection. Nebulised antibiotics can be useful. Sadly, due to the repeat usage of antibiotics, many CF sufferers have very resistant strains of bacteria, especially Pseudomonas aeruginosa. Often the patient will need to be on quinolones and aminoglycosides to deal with these infections.
- Nutrition - Since malabsorption is a big problem, you need to bulk up two things; enzymes, and nutrients.
- Enzymes are dealt with by enteric-coated enzymes. Their coating means they survive the gastric acid, and get released in the duodenum, like they would if they came out of the pancreas. The key missing enzymes are lipases, which presents as poor weight gain and horrible stools.
- Nutrients are managed by CF sufferers taking a lot of extra vitamins and supplements, and aim to eat about an extra 25% of calories, and replacing Vitamins D, E, A and K; all the fat soluble ones.
- Postural Drainage - To clear off the worst of the mucus, to aid in clearing the lungs, most CF sufferers do around 30 minutes of postural exercises, designed to aid the body in naturally removing excess mucus.
- Oxygen - in the later stages of lung failure, the patient will need to be on oxygen, just to adequately oxygenate their body.
- Organ transplant - in some cases, lung transplant has been very successful in curing CF. Sadly, there is a scarcity of lung donors. On the plus side, the new lungs are never affected by the mucus problems of CF, since they have different genes, being from a different person.
Prognosis
It generally means early death. Basically, either the pneumonias get you, or the lung scaring gets you. Survive through that, and you have pancreatitis, and liver failure to deal with. Get through that, and you just need to fight a troll, and solve world hunger. Average life expectancy is hard to estimate. In the worse affected cases, babies can dies of meconius ileus, then you get mild cases living to 60. Median survival, for a baby born now, is around 40ish.