Teaching Case

A 63-year-old male with a medical background of allergic rhinitis reported a deteriorating productive cough characterised by the presence of mucus in the sputum. The cough was accompanied by fatigue and muscle pain. He also reported a 5 kg weight loss within the past 6 months. Blood tests revealed an increase in eosinophils in the peripheral blood and an elevation in C-reactive protein (CRP) levels. An increase in bronchoalveolar lavage (BAL) fluid eosinophils (44%) was also found. The physician ordered a chest x-ray, followed by a chest CT scan.

Chest x-ray showed bilateral upper-lobe consolidations, as well as a peripheral consolidation in the middle third of the right lung.

Chest CT revealed bilateral upper lobe consolidations with air bronchogram surrounded by ground-glass opacities. A peripheral area of consolidation was also found on the lateral segment of the middle lobe.

Eosinophilic pulmonary diseases are rare entities characterised by alveolar and interstitial eosinophilic infiltration. These diseases include acute eosinophilic pneumonia (AEP) and chronic eosinophilic pneumonia (CEP) [1].

AEP is associated with an acute hypersensitivity reaction to an inhaled agent. Tobacco smoke and dust/smoke inhalation are the most common precipitants. Patients are typically around 20 years old and have no history of allergic disease. Clinically, patients typically present with an acute-onset dyspnoea, a non-productive cough, and fever, starting days after the inhalation episode. Severe hypoxemia, respiratory failure, and acute respiratory distress syndrome (ARDS) can also occur. Blood tests show leukocytosis and an elevated CRP. Peripheral eosinophilia is an uncommon finding [2]. Diagnosis is made after a BAL showing eosinophilia, typically >40%. Bilateral ground grass opacities accompanied by areas of consolidation are the most common chest radiography findings. Chest CT often shows an upper lobe predominant pattern of bilateral ground-glass opacities and interlobular septal thickening. Areas of consolidation, centrilobular nodules, and bilateral pleural effusion are also common findings [3]. Treatment involves systemic corticotherapy and respiratory support. If smoking is discontinued, recurrence is rare, and there is rarely a lasting impairment in pulmonary function tests (PFTs).

CEP typically occurs in 30- to 50-year-old patients with a history of allergic disease. There is no association with tobacco use. Dyspnoea, productive cough, wheezing, weight loss, and chest pain typically develop over several months. Peripheral eosinophilia is a common finding, associated with an elevation in IgE and CRP. Unlike AEP, the BLA may not be necessary for diagnosis as long as peripheral eosinophilia above 1000/mm³ is present. PFTs may show a restrictive (more common) or obstructive pattern. Bilateral peripheral consolidations in a “reverse batwing” pattern may be found in chest radiography. On chest CT, the most common findings include bilateral peripheral ground-glass opacities, often associated with areas of consolidation. Despite there not being formal diagnostic criteria, diagnosis is often made based on clinical symptoms, eosinophilia (peripheral and/or BAL), and suggestive imaging findings. Corticosteroids are the treatment of choice. More than half of patients relapse, especially after treatment discontinuation. PFTs often remain altered long after treatment [4,5].

The distinction between AEP and CEP should be made by correlating the epidemiological and clinical settings with imaging and laboratory findings, given that there are no formal diagnostic criteria for either. Despite having similar treatment, these diseases have a significantly different prognosis.

In this case, given that the patient had an allergic background, no history of tobacco use or dust/smoke inhalation, peripheral eosinophilia, a later-found elevated bronchoalveolar lavage eosinophil count (44%), and the above-mentioned imaging findings, the final diagnosis of chronic eosinophilic pneumonia was achieved.