Case #10 - Respiratory Failure in a 7-Month-Old Black Female

Authors: Sabina Ali, MD; Rosa A Vidal, MD; Sheryl Falkos, MDSeries Editors: Rosa A Vidal, MD; Sheryl Falkos, MD


June 23, 2004

A Review of Cystic Fibrosis (CF)

Q: What is CF?

CF is an inherited disease that is a significant cause of severe respiratory disease and failure to thrive in the pediatric population. It is an autosomal recessive disorder in which carriers of the gene are asymptomatic. Carrier couples have a 1 in 4 chance (25%) of producing an affected baby with each pregnancy.

The CF gene has been identified on the long arm of chromosome 7. There are more than 800 mutations described in the CF transmembrane regulator (CFTR) gene, which result in failure of the cAMP chloride channel transport mechanism. CFTR is a glycoprotein located at the apical region of epithelial cells in a variety of organ systems including airways, intestines, pancreatic ducts, and bile ducts.[1] Not all CFTR mutations cause CF, and expression of the disease is extremely variable even within affected members of the same family.[2]

CF is most often thought of as a disease affecting those of Caucasian descent. However, it can be seen in a variety of ethnic groups, albeit with less frequency:

Caucasian (non-Hispanic/non-Ashkenazi Jewish): 1 in 25
Ashkenazi Jewish: 1 in 25
Hispanic: 1 in 46
African-American: 1 in 65
Asian: 1 in 90[3]

This patient's immediate family members were all of African-American descent. Her siblings were growing well and had no history of persistent illnesses or hospitalization. There was no history of CF or pediatric deaths in the family.

The key to diagnosis of CF is first to have a high index of suspicion. Children who present with failure to thrive with or without respiratory symptoms should have a sweat chloride test performed as part of their work-up, regardless of race or family history.

Q: Which organ systems are most commonly involved in CF?

CF principally involves the respiratory, gastrointestinal, and hepatobiliary tracts. The most common symptoms are cough, wheezing, and pneumonia. Airway obstruction with increased production of mucus and recurrent infections (Staphylococcus aureus, Haemophilius influenzae, and Pseudomonas aeruginosa) result in progressive deterioration of lung function. Recurrent bowel obstruction, intussusception, and rectal prolapse are gastrointestinal tract complications that can present in patients with CF. Pancreatic insufficiency, resulting in protein and fat malabsorption, may present in infancy.[1]

Q: How is CF diagnosed?

The "gold standard" diagnostic test for CF has historically been the sweat chloride test (> 60 mEq/L). However, genetic diagnosis is now available as a confirmation in equivocal cases to increase accuracy of diagnosis. Identification of 2 abnormal CFTR alleles is diagnostic of CF.[1,4,5]

There are prenatal screening programs available for CF. Prenatal testing can now be accomplished in most families with an affected member. The testing is conducted through mutation analysis of fetal cells obtained by chorionic villus sampling (10 weeks' gestation) or through samples obtained via amniocentesis (15 to 18 weeks). This type of screening is not routinely offered.

However, prenatal screening should be offered to: (1) adults with a family history of CF, (2) reproductive partners of individuals with CF, (3) couples in whom 1 or both are Caucasian (including Ashkenazi Jews) and are planning a pregnancy, and (4) couples in whom 1 or both are Caucasian (including Ashkenazi Jews) and are seeking prenatal care. Screening should also be made available to couples where 1 or both partners are not Caucasian or Ashkenazi Jews.[4,5]

Q: What treatments are needed in the care of patients with CF?

Appropriate treatment improves the health and life expectancy in CF patients. The goal of therapy is to prevent or slow the progression of airway damage. Treatment is designed to control airway infection and inflammation and to reduce mucus accumulation. Viral infection is prevented with vaccination.[6]

Patients often present with pulmonary exacerbations which, depending on the severity of symptoms, are treated either in the home or hospital. Treatment regimens usually consist of oral or intravenous antibiotics. Tobramycin, administered through intermittent inhalation therapy, is commonly used. Mild exacerbations may be treated at home with oral antibiotics and continuation of the patient's regimen of chest physiotherapy.

Severe exacerbations typically require hospitalization and the use of multiple intravenous antibiotics. Choice of antibiotics is based on previous culture results or, if these are unknown, is aimed at the most common pathogens causing pulmonary disease in this patient population. These include Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa.

Chest physical therapy with postural drainage is recommended at a frequency of 1 to 4 times a day, depending on severity of illness, to aid in the clearance of mucus from the airways. Corticosteroids and bronchodilators are commonly used as part of daily treatments or during pulmonary exacerbations.

Pancreatic enzyme replacement and fat-soluble vitamin supplementation is needed in CF patients. Pharmacologic gastric acid suppression helps patients achieve adequate fat absorption and maintain adequate nutrition.[1]

Q: What is the most significant factor in prolonging the survival of patients with CF?

Optimal nutritional status, physical fitness, and aggressive treatment of pulmonary exacerbations have been most significantly associated with improved survival. CF patients have difficulty in gaining weight because of malabsorption of fat and protein with fat-soluble vitamin deficiency. Those patients who fail maximum nutritional therapy and are persistently malnourished may require nocturnal gastrostomy or jejunostomy tube feedings.[7]

Overall, the prognosis of patients with CF has dramatically improved in the past few decades. Median survival increased from 14 to 28 years between 1969 and 1990. Female patients have lower survival than male patients (25 vs 30 years of age, according to a study conducted in 1990).[8]


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