Cystic fibrosis (CF) is a life threatening genetic disease, which affects the lungs and digestive system. About 30,000 children and adults in the United States and 70,000 people worldwide have cystic fibrosis. CF is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. It makes a protein that is inserted into the membranes of the cells that line the inner surfaces of organs. The CFTR gene forms channels that regulate the movement of salt and water in and out of cells. Mutations can affect how the body secretes sweat, tears, digestive juices, and mucus. The CFTR gene codes for a protein that helps move salt and water through cells. Defects in this gene produce an unusually thick and sticky mucus that builds up in the body and damages the lungs, pancreas, and other organs. These fluids are normally thin and slippery, which allows it to act as a lubricant. The mucus can block the lungs, which leads to lung infections, as well as obstruct the pancreas and stops natural enzymes from helping the body break down food and absorb vital nutrients. People with CF are expected to live into at least their 30s or 40s, and sometimes even beyond.
CF is inherited recessively, so a person has to inherit a copy of the mutated CFTR gene from both parents in order to get the disease. It is most common in European or Jewish ancestry, where one in every 30 people carry the mutation. There are more than 500 known mutations of the CFTR gene that can cause CF, and most of them are extremely rare. Because there are so many different CFTR mutations that can cause CF and so many variations of having two mutated copies, it is possible for a person to have severe lung and pancreatic diseases or only one of the two.
The symptoms of CF vary, and symptoms may not even be visible until late into the teen years or adult years if the disease is mild. Symptoms and severity can vary overtime as well. As CF gets more severe, people show more severe symptoms, and lung function can decline, which can cause severe breathing problems. Most people with CF die due to respiratory failures. Symptoms include very salty tasting skin, persistent coughing and phlegm, frequent lung infections, wheezing, shortness of breath, poor growth, slow weight gain, and frequent greasy bulky stools.
Knowing the exact mutations in the CFTR gene allow for better treatment. Current treatment concentrates mostly on thinning the mucus to make it more lubricant, treating the infections it causes, and providing sufficient nutrition.
Most hospitals screen newborns for CF by testing the levels of certain enzymes in dried spots of blood. Babies that test positive are given additional tests to confirm CF. Ivacaftor, a drug that treats CF, treats people with the G551D mutation, which is a gating mutation. Gating mutations prevent the CFTR protein from opening and closing, which do not allow it to act as an ion gate.
The 23andMe report determines the presence or absence of 26 of the most common CFTR mutations. 21 of these are included in the mutations that are currently recommended for CF carrier testing by the American College of Medical Genetics. It is possible to have one of the other 500 mutations that are not assessed in the report. Furthermore, if you are concerned about cystic fibrosis you should consult a medical professional.
CF is inherited recessively, so a person has to inherit a copy of the mutated CFTR gene from both parents in order to get the disease. It is most common in European or Jewish ancestry, where one in every 30 people carry the mutation. There are more than 500 known mutations of the CFTR gene that can cause CF, and most of them are extremely rare. Because there are so many different CFTR mutations that can cause CF and so many variations of having two mutated copies, it is possible for a person to have severe lung and pancreatic diseases or only one of the two. Carrier rates in Caucasians, which include Ashkenazi Jews, are one in 29, one in 46 in Hispanic Americans, one in 65 in African Americans, and one in 90 in Asians.
CFTR mutations also affect the reproductive system, one of which is congenital bilateral absence of the vas deferens (CBAVD). Infertile men with low sperm count and the presence of one CFTR mutation are most likely carrying a second unreported mutation on the CFTR gene. The most common CFTR mutations is the deltaF508 mutation, which about half the people with CF in the United states have two copies of. People with two copies of this mutation usually have more severe symptoms than those who have only one copy.