ANSWER 3
The chest X-ray shows abnormal shadowing throughout both lungs, more marked in both
upper lobes with some ring shadows and tubular shadows representing thickened bronchial
walls. These findings would be compatible with a diagnosis of bronchiectasis. The pul-
monary arteries are prominent, suggesting a degree of pulmonary hypertension. The distri-
bution is typical of that found in cystic fibrosiswhere the changes are most evident in the
upper lobes. Most other forms of bronchiectasis are more likely to occur in the lower lobes
where drainage by gravity is less effective. High-resolution computed tomography (CT) of
the lungs is the best way to diagnose bronchiectasis and to define its extent and distribu-
tion. In younger and milder cases of cystic fibrosis, the predominant organisms in the spu-
tum are Haemophilus influenzaeandStaphylococcus aureus. Later, as more lung damage
occurs,Pseudomonas aeruginosais a common pathogen. Once present in the lungs in cys-
tic fibrosis, it is difficult or impossible to remove it completely.
Cystic fibrosis should always be considered when there is a story of repeated chest infec-
tions in a young person. Although it presents most often below the age of 20 years, diag-
nosis may be delayed until the 20s, 30s or even 40s in milder cases. Associated problems
occur in the pancreas (malabsorption, diabetes), sinuses and liver. It has become evident
that some patients are affected more mildly, especially those with the less common genetic
variants. These milder cases may only be affected by the chest problems of cystic fibrosis
and have little or no malabsorption from the pancreatic insufficiency.
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The differential diagnosis in this young man would be other causes of diffuse
bronchiectasis such as agammaglobulinaemia or immotile cilia. Respiratory function
should be measured to see the degree of functional impairment. Bronchiectasis in the
upper lobes may occur in tuberculosis or in allergic bronchopulmonary aspergillosis
associated with asthma.Differential diagnosisThe common diagnostic test for cystic fibrosis is to measure the electrolytes in the sweat,
where there is an abnormally high concentration of sodium and chloride. At the age of
19 years, the sweat test may be less reliable. It is more specific if repeated after the adminis-
tration of fludrocortisone. An alternative would be to have the potential difference across
the nasal epithelium measured at a centre with a special interest in cystic fibrosis. Cystic
fibrosis has an autosomal recessive inheritance with the commonest genetic abnormality
"F508 found in 85 per cent of cases. The gene is responsible for the protein controlling
chloride transport across the cell membrane. The commoner genetic abnormalities can be
identified and the current battery of genetic tests identifies well over 95 per cent of cases.
However, the absence of "F508 and other common abnormalities would not rule out cys-
tic fibrosis related to the less common genetic variants.
In later stages, lung transplantation can be considered. Since the identification of the
genetic abnormality, trials of gene-replacement therapy have begun.
- Milder forms of cystic fibrosis may present in adolescence and adulthood.
- Milder forms are often related to less common genetic abnormalities.
- A high-resolution CT scan is the best way to detect bronchiectasis and to define its extent.