Cystic Fibrosis (CF) updated 11/2019
CF is a life threatening hereditary disorder that results in a thick build-up of sticky mucus primarily affecting the respiratory and digestive systems. Other areas of the body such as sweat glands, the pancreas, liver and sex organs can be impacted as well. Some 30,000 American men, women and children exhibit this orphan disease with approx. 1,000 new cases of CF diagnosed each year.
Screening of newborns for cystic fibrosis is now performed in every state in the United States. As a result, the condition can be diagnosed within the first month of life, before symptoms develop.
Cystic Fibrosis is caused by one or more mutations (changes) in the CFTR gene on chromosome number 7 which controls the movement of salt (chloride ions) and water into and out of the body’s cells. It is a recessive (hidden) gene carried by millions of American’s, often without their knowledge. However, when two parents, each with a faulty CFTR gene, mate, there is a 1 in 4 chance that their child will develop cystic fibrosis. Approximately 75% of CF patients are diagnosed by age 2 while some, with a milder version of the disease, are not detected until their late teens.
When a CFTR gene mutation occurs, water movement at the cellular level is reduced and salt builds up producing thick sticky mucus that clogs many of the body’s ducts and tubes preventing them from functioning normally. One of the tell tale symptoms of CF is salty tasting sweat which is why the sweat test to determine the level of chloride ions is the basis for diagnosing this disease. This loss of salt can lead to other complications such as dehydration, decreased blood pressure, increased heart rate, weakness and fatigue.
The two organs most affected in CF patients are the lungs and pancreas. Shortness of breath, persistent coughing and frequent lung infections occur when the respiratory system is impacted. Because the mucus clogs the tubes leading from the pancreas to the intestine, CF patients have difficulty digesting food and absorbing those nutrients necessary for maintaining normal health. Symptoms of malabsorption include poor weight gain, foul smelling stools, stomach ache and gas.
The underlying causes of Cystic Fibrosis Related Diabetes (CFRD) are not well understood and differ from the causes of type 1 and type 2 diabetes. CFRD is due to a decrease in the level of circulating insulin resulting from B cell self destruction coupled with a reduction in insulin secretion by the remaining beta cells. The present belief is that these impacted beta cells lose their ability to sense changes in sugar levels leading to poorly regulated insulin production. . Future insights as to how the CF chloride-channel regulates beta cell insulin secretion may someday lead to a better understanding and treatment for other forms of diabetes including Brittle Diabetes. CFTR genotypes most often seen are those generally associated with EPI – exocrine pancreatic insufficiency. Please refer to our article on chronic pancreatitis for more information. This variation in degree of CF severity together with EPI can, at times, result in uncontrollable blood glucose levels or brittleness.
25% of CF patients will develop diabetes in their teens and almost 50% will develop diabetes by age 30. Women with CF will develop diabetes 7 years earlier than men. Although the reasons are still unclear hormonal gender differences and the use of oral contraceptives are possible explanations. The marked increase seen today in CFRD is due to the fact that medical advances in the treatment of CF has extended people’s lives to an average age of 41 with some living into their late forties and fifties. CFRD affects 2% of CF children, 19% of CF adolescents, 40% of CF young adults, and is seen in nearly 50% of CF patients over the age of 30. Both morbidity ( the prevalence of disease in a population) and mortality (death) rates are greater in CFRD patients compared to those with CF without diabetes. However, mortality in CFRD is almost always due to more rapid progression of lung disease and not vascular complications of diabetes. One of the unanswered questions is what prevents the other 50% from ever developing diabetes. An oral glucose tolerance test is recommended to diagnose CFRD.
Diet advice for CFRD patients is much different than for other forms of diabetes. The CFRD patient must maintain a high caloric diet, but one low in simple sugars in order to maintain weight. This requires that a tailored and strict insulin regimen be maintained.
The symptoms and severity of CF worsen with time. Symptoms that may be noticed later in life include infertility in men, pancreatitis, clubbed fingers and a variety of respiratory symptoms and infections. For those experiencing CFRD, complications due to diabetes, neuropathy (nerve), nephropathy(kidney) and retinopathy (retina) can occur as well.
Kalydeco is a prescription medicine used for the treatment of CF in patients 6 and older whose specific mutation in their CF genes happens to respond well to this prescription drug. For several other CF gene mutations, this drug has been found to be ineffective.
Notes: A) Oxidative stress at the cellular level is now recognized as a common factor in the development of type 1 , type2 and CFRD. More research into the functioning of this potential key mechanism is needed. B) Unfortunately, at this time, there is no cure for CF.