Lung - Cystic Fibrosis - Erler Zimmer
Clinical History
A 6-year-old girl was admitted with symptoms including a productive cough, dyspnea, and fevers. Despite increasing hypotension, she succumbed shortly after admission. Her medical history included recurrent pneumonia and meconium ileus, and the clinical diagnosis was cystic fibrosis (mucoviscoidosis). Tragically, her sister also passed away at the age of 3 from the same disease.
Pathology
The lung parenchyma exhibits extensive changes primarily with a bronchial distribution. Many bronchi are dilated (bronchiectasis) and filled with thick, yellowish, purulent material. These changes are most pronounced in the upper lobe, where a small focus of 'honeycomb' change is also present at the apex. Multiple abscesses are observed, particularly in the basal and central parts of the lower lobe. The base of the lower lobe shows severe fibrosis and consolidation, with very little normal lung tissue remaining. These pathological changes are characteristic but not pathognomonic of cystic fibrosis.
Further Information
Cystic fibrosis (CF) is an inherited disorder affecting chloride ion transport, caused by mutations in the cystic fibrosis conductance regulator (CFTR) gene on chromosome 7. These mutations lead to defects in the chloride channel protein, resulting in dysfunctional chloride channels. The consequences include increased water absorption in exocrine glands and epithelium of the respiratory, gastrointestinal, and reproductive tracts. Dehydrated viscous secretions obstruct these passages, causing clinical features such as persistent pulmonary infection, pancreatic insufficiency, liver cirrhosis, intestinal obstruction, male infertility, and elevated sweat chloride levels. In the airway, CF patients experience decreased chloride secretion, increased water reabsorption, dehydrated mucous lining, defective mucociliary action, mucous obstruction, bronchiole dilatation (bronchiectasis), and secondary infection. Common bacteria causing lower respiratory tract infections in CF patients include Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas. Chronic bronchitis and bronchiectasis are common, with pulmonary issues being the leading cause of mortality. The average life expectancy in developed countries is between 40-50 years.
CF occurs in approximately 1 in 3000 live births, inherited in an autosomal recessive pattern. It is most prevalent in fair-skinned populations, with 1 in 20 individuals being carriers of the gene. Symptoms may manifest in-utero or up to adolescence, depending on the disease's severity. Neonatal screening tests, such as the immunoreactive trypsinogen test, are commonly used for diagnosis. A positive screening result is followed by a formal diagnosis using a sweat test that shows chloride levels exceeding 60mmol/L.
