Late diagnosis of cystic fibrosis: A case-based radiological approach

A 20-year-old male with a history of recurrent lower tract infections arrived at the hospital with cough and low-grade fever (38.6 C), at physical examination fine rales at the right lung base were evident, for which a chest X-ray and a high-resolution computed tomography (HRCT) were performed. 

A Posteroanterior (PA) chest X-ray was performed showing diffuse bronchiectasis, predominantly at lower lobes, with ground-glass opacities at the right lung base, and pulmonary hyperinflation (Fig 1).

To characterized better the lesions, a chest HRCT was performed, showing bilateral centrally distributed cystic bronchiectasis associated with mucous plugging, moreover, ground-glass opacities and tree-in-bud pattern at the lateral segment of the right lower lobe are seen, suggesting an inflammatory disease of the distal airway (Fig 2).

Based on the patient's clinical history and the radiological findings, the initial diagnosis was residual post-infectious bronchiectasis versus cystic fibrosis (CF). The final diagnosis was confirmed with a sweat chloride test supporting CF.

CF is an autosomal recessive inherited disease caused by dysfunction of the chloride channels of exocrine glands, specifically the CF transmembrane conductance regulator (CFTR) protein [1–3]. The mutation leads to a decrease in chloride secretion and an increased sodium absorption which reduces the amount of water from secretions, making them more viscous [1].

CF is a multisystemic condition with a worldwide incidence of 1:2500 live births [3], the classic disease is mainly diagnosed in the first 3 years of life, however, late diagnosis may occur in some atypical variants, which manifests as a milder disease usually affecting 1 organ system [3,4,5].

When CF is diagnosed in adults, the clinical presentation differs from paediatrics, mainly presenting as chronic superinfected bronchiectasis, usually caused by pathogens such as Pseudomonas aeruginosa [6,7], which is responsible for more than 90% of fatal events [3,5].

The advances in image modalities have highly contributed to increasing the clinical suspicion of CF in adults, mainly through the visualization of lung hyperinflation, lobar collapse, pulmonary hypertension, and bronchiectasis with diffuse distribution, which are initially cylindrical with progression to varicose and cystic bronchiectasis (Fig 3) [8]. The acute complications of CF are mainly lobar pneumonia and pneumothorax. Several studies have described the Brasfield and Wisconsin scoring systems, which are useful to assess CF severity on chest X-ray with a good interobserver agreement, nevertheless, it is time-consuming [9].

It is important to interpret the detection of mucous plugging in chest HRCT as a trigger for pulmonary infections, being highly effective to predict exacerbations [8].

The gold standard for CF diagnosis is the sweat chloride test, being suggestive when the result is between 40-60 mEq/L and positive if > 60 mEq/L, nevertheless, patients with atypical cystic fibrosis may or may not have elevated sweat chloride test, for which a genetic analysis must be performed [2,5].

The mainstay of treatment is respiratory therapy plus dornase alfa, recently the usage of CFTR modulators such as ivacaftor and lumacaftor have demonstrated benefits [10]. Angiography is reserved for bronchial artery embolization in patients with severe hemoptysis [11]. The prognosis of CF has improved in recent years, presenting an average life expectancy of 50 years [9], however, it seems to be better when the disease is diagnosed in adulthood [3].

Teaching point: The diagnosis of CF should not only be considered in children but also in adults, especially if the clinical history reveals recurrent pneumonia and diffuse bronchiectasis in HRCT.

Written informed patient consent for publication has been obtained.