Cystic fibrosis is the most common fatal and inherited disease in Caucasian populations, caused by the acquisition of two recessive genes from carriers who are typically not affected themselves. The abnormality affects the so-called exocrine glands and the most obvious and troublesome feature is the development of chronic infections of the respiratory tract. Many organ systems are affected by the glandular abnormalities but it is the eventual failure of the respiratory system which is the most common cause of death.
The genetic abnormality affects the thickness of the body’s mucus, making it stickier which in turn makes it more vulnerable to bacterial infection. Thickened secretions can be present in the respiratory tract which makes them difficult to clear, but they are also present in the pancreas, sweat glands and the digestive tract. Initially the lungs are normal but soon after birth an infection develops at some time and the cycle of infection and inflammation is set up along with a continual presence of specific bacteria in the lungs. Gradually the lung membranes become thickened and less efficient, leading eventually to respiratory failure.
Thickened mucus secretions in the intestinal tract can cause an obstruction of some part of the bowel and the ability to absorb nutrients from food is also reduced, often indicated initially by the baby failing to gain weight normally (“failure to thrive”). If this progresses and adhesions form then the bowel can become obstructed, necessitating removal of part of its length which further reduces nutrient absorption. Pancreatic enzymes are unable to work at optimal efficiency, and if pancreatic insufficiency develops then patients may fail to gain weight and poorly absorb vitamins which are fat soluble such as A, D, E and K.
In terms of frequency cystic fibrosis is the most commonly occurring inherited condition which has a fatal outcome, inherited as a recessive gene trait. Typical incidence in white European populations is one in 3200 while Asian populations may only see one in 90,000 children born. Typical survival age for adults is around 37 years, with males living on average significantly longer than females. The lung changes progress from bronchitis to bronchiectasis and then to end stage lung disease with heart failure. The way the disease progresses, how old the person is at the diagnosis, how severe the symptoms are and how fast the disease progresses are all very variable.
Inflammation of the gallbladder and the presence of gallstones are higher in people with cystic fibrosis than the typical population. Puberty and development of secondary sexual characteristics are typically delayed, with infertility in males due to the lack of formation of a vas deferens, while female fertility may be reduced to some extent. Coming from a social layer with low socioeconomic status is associated with significantly worse lung disease outcomes. Males are less severely affected by lung symptoms than females, with females having more severe progression of lung disease and a younger age at death.
Due to the complexity of cystic fibrosis and the involvement of many bodily systems the most effective diagnosis and management of this condition is performed by a multidisciplinary team in a specialist centre. Apart from the initial diagnosis and baseline measurements, followed by the plan of treatment, there are many other parts to the overall management. Education of the patient or the parents is of vital importance as adherence to the treatment regime is so important if the patient is to make the best of their remaining life. Counselling may be employed as patients face the difficulties of managing a lifelong condition. Physiotherapy instruction for airway clearance technique is also vital, with instruction on how to use inhalers and nebulisers.
The complications of respiratory disease may need surgical management to treat such conditions such as collapsed lung or considerable coughing up of blood. Gastrointestinal complications and obstruction may also need to be managed surgically. End stage lung disease can be managed by lung transplant or heart-lung transplant, but transplants may not increase life expectancy although quality of life may be improved. The diet can be essentially normal with an increased energy and fat intake recommended with supplementation of vitamins and minerals. Malabsorption of nutrients and the increased nutrient demand of having chronic inflammation require nutritional supplementation.
Author: Jonathan Blood-Smyth