In clinical work, eosinophilic pneumonias are a heterogeneous group of diseases characterized by pulmonary eosinophilia, pulmonary infiltrates and/or pulmonary dysfunction and often blood eosinophilia.
Eosinophilic pneumonias may be idiopathic or associated with other disorders or other known factors.
Clinically, the disease may be chronic or acute and even life-threatening.
Think of the possibility of eosinophilic pneumonia in a patient with pneumonia
not responding to treatment
associated with eosinophilia
with systemic symptoms, such as cardiac symptoms or a rash.
Classification
Eosinophilic pneumonias can be classified into
idiopathic
secondary
associated with other disorders.
Symptoms
Cough, sharp chest pain, dyspnoea
Fever
In chronic forms of the disease also weight loss and fatigue
Idiopathic eosinophilic pneumonia
Acute idiopathic eosinophilic pneumonia
Symptoms develop in a few days in an originally healthy young adult.
May be associated with changes in smoking habits but one patient in three is non-smoking.
May also develop after various kinds of respiratory exposure (smoke or fumes, soil (plant-repotting), dust (household renovation), etc.).
One or more patchy infiltrates on chest x-ray, and possibly pleural effusion.
Leukocytosis but not necessarily eosinophilia
Often hypoxaemia
The diagnosis can be confirmed by high-resolution computed tomography of the lungs and bronchoscopy with bronchoalveolar lavage (BAL).
Glucocorticoids (e.g. 1 to 2 mg/kg/day prednisolone for 6 to 8 weeks, gradually reducing the dose) give a rapid response.
No relapses.
Chronic idiopathic eosinophilic pneumonia
Symptoms develop slowly, within several weeks or months.
The disease is often preceded by asthma and chronic sinus problems.
Chest x-ray shows one or more peripheral patchy infiltrates that may shift position.
Elevated CRP and ESR, often also IgE, neutrophilia, anaemia, often eosinophilia
The diagnosis can be confirmed by high-resolution computed tomography of the lungs and bronchoscopy with bronchoalveolar lavage (BAL).
Glucocorticoid treatment (e.g. prednisolone) at a dosage of 0.5 mg/kg often leads to resolution of the changes in the chest x-ray within as little as a week. Treatment with decreasing doses should be continued for 6 to 12 months.
More than half of the patients have relapses.
Hypereosinophilic syndrome
Blood eosinophil levels repeatedly exceeding 1.5 × 109 /l and clinically significant organ damage
The most common target organs in addition to the lungs are:
May be due to drugs, parasites, mycobacterial infection, fungi (allergic bronchopulmonary aspergillosis), radiotherapy or toxic agents (e.g. inhaled illegal drugs).
The symptoms of drug reaction may begin within a few hours but, most commonly, within several weeks or months after the beginning of medication.
The delay between the eosinophilic manifestation caused by some parasites and the original infection may be months or years. A careful travel history is always necessary when investigating eosinophilia.
Patchy lesions are commonly seen in the chest x-ray; pleural effusion may also be present.
Treatment depends on the aetiology. If a drug reaction is suspected, withdrawal of the medication is the primary form of treatment.
If symptoms are severe, glucocorticoids may be indicated.
In parasitic diseases the specific treatment is selected on the basis of the causative agent. Consulting a specialist in infectious diseases is advisable.
Eosinophilic pneumonia associated with other diseases
Eosinophilic granulomatosis with polyangitis (Churg-Strauss)
Cottin V. Eosinophilic Lung Diseases. Clin Chest Med 2016;37(3):535-56. [PubMed]
Allen J, Wert M. Eosinophilic Pneumonias. J Allergy Clin Immunol Pract 2018;6(5):1455-1461. [PubMed]
De Giacomi F, Vassallo R, Yi ES ym. Acute Eosinophilic Pneumonia. Causes, Diagnosis, and Management. Am J Respir Crit Care Med 2018;197(6):728-736. [PubMed]