1. A. Rovescalli
1. Department of Pathology The University Medical School of Milan
Dr. A. Milunsky describes (Pediatrics, 42:501, 1968) the observation "for the first time" of cystic fibrosis of the pancreas in three children with Down's syndrome. I would like to point out that such association has been observed in several autopsied cases at the Department of Pathology in University Medical School of Milan. I think this association occurs very frequently in Down's syndrome, and I described it in the book "Il Mongolismo, auxopatia somatopsichica caniotipica," by E. Aldeghi and A. Maderna, in the chapter devoted to the pathological anatomy of the syndrome
* Copyright C 1969 by the American Academy of Pediatrics
What is Cystic Fibrosis?
Cystic fibrosis (also known as CF or mucoviscidosis) is a common recessive genetic disease which affects the entire body, causing progressive disability and often early death. The name cystic fibrosis refers to the characteristic scarring (fibrosis) and cyst formation within the pancreas, first recognized in the 1930s. Difficulty breathing is the most serious symptom and results from frequent lung infections that are treated with, though not cured by, antibiotics and other medications. A multitude of other symptoms, including sinus infections, poor growth, diarrhea, and infertility result from the effects of CF on other parts of the body.
CF is caused by a mutation in the gene for the protein cystic fibrosis transmembrane conductance regulator (CFTR). This gene is required to regulate the components of sweat, digestive juices, and mucus. Although most people without CF have two working copies of the CFTR gene, only one is needed to prevent cystic fibrosis. CF develops when neither gene works normally and therefore has autosomal recessive inheritance.
CF is most common among Caucasians; one in 25 people of European descent carry one allele for CF.
Ireland has both the highest incidence of CF in the world; 2.98 per 10,000 - and the highest carrier rate in the world with 1 in 19 individuals classed as carriers. Cystic fibrosis is Ireland's most common life-threatening inherited disease. Ireland also has the largest proportion of families with more than one child suffering from CF.
Approximately 30,000 Americans have CF, making it one of the most common life-shortening inherited diseases in the United States.
Individuals with cystic fibrosis can be diagnosed before birth by genetic testing, or by a sweat test in early childhood. Ultimately, lung transplantation is often necessary as CF worsens.
What are the symptoms of CF?
The hallmark symptoms of cystic fibrosis are salty tasting skin, poor growth and poor weight gain despite a normal food intake, accumulation of thick, sticky mucus, frequent chest infections and coughing or shortness of breath. Males can be infertile due to congenital absence of the vas deferens. Symptoms often appear in infancy and childhood, such as bowel obstruction due to meconium ileus in newborn babies. As the child grows, he or she will need to exercise to release mucus in the alveoli. Ciliated epithelial cells in the patient have a mutated protein that leads to abnormally viscous mucus production. The poor growth in children typically presents as an inability to gain weight or height at the same rate as their peers and is occasionally not diagnosed until investigation is initiated for poor growth. The causes of growth failure are multi-factorial and include chronic lung infection, poor absorption of nutrients through the gastrointestinal tract, and increased metabolic demand due to chronic illness.
In rare cases, cystic fibrosis can manifest itself as a coagulation disorder. Young children are especially sensitive to vitamin K malabsorptive disorders because only a very small amount of vitamin K crosses the placenta, leaving the child with very low reserves. Because factors II, VII, IX, and X (clotting factors) are vitamin K–dependent, low levels of vitamin K can result in coagulation problems. Consequently, when a child presents with unexplained bruising, a coagulation evaluation may be warranted to determine whether there is an underlying disease.
Lung and sinus
Respiratory infections in CF patients varies according to age.
Green = Pseudomonas aeruginosa
Brown = Staphylococcus aureus
Blue = Haemophilus influenzae
Red = Burkholderia cepacia complex
Lung disease results from clogging of the airways due to mucus build-up, decreased mucociliary clearance and resulting inflammation. Inflammation and infection will cause injury and structural changes to the lungs, leading to a variety of symptoms. In the early stages, incessant coughing, copious phlegm production, and decreased ability to exercise are common. Many of these symptoms occur when bacteria that normally inhabit the thick mucus grow out of control and cause pneumonia. In later stages, changes in the architecture of the lung such as pathology in the major airways (bronchiectasis) further exacerbate difficulties in breathing. Other symptoms include coughing up blood (hemoptysis), high blood pressure in the lung (pulmonary hypertension), heart failure, difficulties getting enough oxygen to the body (hypoxia), and respiratory failure requiring support with breathing masks such as bilevel positive airway pressure machines or ventilators. Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa are the three most common organisms causing lung infections in CF patients. In addition to typical bacterial infections, people with CF more commonly develop other types of lung disease. Among these is allergic bronchopulmonary aspergillosis, in which the body's response to the common fungus Aspergillus fumigatus causes worsening of breathing problems. Another is infection with Mycobacterium avium complex (MAC), a group of bacteria related to tuberculosis, which can cause a lot of lung damage and does not respond to common antibiotics.
Mucus in the paranasal sinuses is equally thick and may also cause blockage of the sinus passages, leading to infection. This may cause facial pain, fever, nasal drainage, and headaches. Individuals with CF may develop overgrowth of the nasal tissue (nasal polyps) due to inflammation from chronic sinus infections. Recurrent sinonasal polyps can occur in as many as 10% to 25% of CF patients. These polyps can block the nasal passages and increase breathing difficulties.
Cardiorespiratory complications are the most common cause of death (~80%) in patients followed by most CF centers in the United States.
Prior to prenatal and newborn screening, cystic fibrosis was often diagnosed when a newborn infant failed to pass faeces (meconium). Meconium may completely block the intestines and cause serious illness. This condition, called meconium ileus, occurs in 5–10% of newborns with CF. In addition, protrusion of internal rectal membranes (rectal prolapse) is more common, occurring in as many as 10% of children with CF, and it is caused by increased fecal volume, malnutrition, and increased intra–abdominal pressure due to coughing.
The thick mucus seen in the lungs has a counterpart in thickened secretions from the pancreas, an organ responsible for providing digestive juices which help break down food. These secretions block the exocrine movement of the digestive enzymes into the duodenum and result in irreversible damage to the pancreas, often with painful inflammation (pancreatitis). The pancreatic ducts are totally plugged in more advanced cases, usually seen in older children or adolescents. This causes atrophy of the exocrine glands and progressive fibrosis.
The lack of digestive enzymes leads to difficulty absorbing nutrients with their subsequent excretion in the feces, a disorder known as malabsorption. Malabsorption leads to malnutrition and poor growth and development because of calorie loss. Resultant hypoproteinemia may be severe enough to cause generalized edema. Individuals with CF also have difficulties absorbing the fat-soluble vitamins A, D, E, and K.
In addition to the pancreas problems, people with cystic fibrosis experience more heartburn, intestinal blockage by intussusception, and constipation. Older individuals with CF may develop distal intestinal obstruction syndrome when thickened feces cause intestinal blockage.
Exocrine pancreatic insufficiency occurs in the majority (85% to 90%) of patients with CF. It is mainly associated with "severe" CFTR mutations, where both alleles are completely nonfunctional (e.g. ΔF508/ΔF508). It occurs in 10% to 15% of patients with one "severe" and one "mild" CFTR mutation where there still is a little CFTR activity, or where there are two "mild" CFTR mutations. In these milder cases, there is still sufficient pancreatic exocrine function so that enzyme supplementation is not required. There are usually no other GI complications in pancreas-sufficient phenotypes, and in general, such individuals usually have excellent growth and development. Despite this, idiopathic chronic pancreatitis can occur in a subset of pancreas-sufficient individuals with CF, and is associated with recurrent abdominal pain and life-threatening complications.
Thickened secretions also may cause liver problems in patients with CF. Bile secreted by the liver to aid in digestion may block the bile ducts, leading to liver damage. Over time, this can lead to scarring and nodularity (cirrhosis). The liver fails to rid the blood of toxins and does not make important proteins such as those responsible for blood clotting. Liver disease is the third most common cause of death associated with CF.
Clubbing of the fingers in a person with cystic fibrosis
The pancreas contains the islets of Langerhans, which are responsible for making insulin, a hormone that helps regulate blood glucose. Damage of the pancreas can lead to loss of the islet cells, leading to a type of diabetes that is unique to those with the disease. This cystic fibrosis related diabetes (CFRD) shares characteristics that can be found in Type 1 and Type 2 diabetics, and is one of the principal non-pulmonary complications of CF. Vitamin D is involved in calcium and phosphate regulation. Poor uptake of vitamin D from the diet because of malabsorption can lead to the bone disease osteoporosis in which weakened bones are more susceptible to fractures. In addition, people with CF often develop clubbing of their fingers and toes due to the effects of chronic illness and low oxygen in their tissues.
Infertility affects both men and children. At least 97% of men with cystic fibrosis are infertile, but not sterile and can have children with assisted reproductive techniques. These men make normal sperm but are missing the tube (vas deferens), which connects the testes to the ejaculatory ducts of the penis. Many men found to have congenital absence of the vas deferens during evaluation for infertility have a mild, previously undiagnosed form of CF. Some women have fertility difficulties due to thickened cervical mucus or malnutrition. In severe cases, malnutrition disrupts ovulation and causes amenorrhea.