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Eosinophilic Pneumonia

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.

Eosinophilic pneumonias can be classified into
- idiopathic
- secondary
- associated with other disorders.

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.

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.

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:
- heart: arrhythmias, cardiac failure, valve disease, pericarditis, thromboembolism
- nervous system: peripheral nerve damage, neuropathic pain, hemiplegia
- skin: various types of rash.

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.

See Vasculitides Vasculitides.
Patients often have severe asthma and allergic rhinitis. Extrapulmonary manifestations of the disease often lead to the right diagnostic track.
Tissue biopsy specimens show eosinophilic arteritis and granulomas.
ANCA antibodies (antineutrophil cytoplasmic antibodies) are positive in 40% of patients.
Oral glucocorticoids should be used primarily.

If the response to glucocorticoids is poor, the possibility of malignancy should be kept in mind.
Examinations: clinical examination, mammography, gynaecological examination; CT should be considered.

Camus P. Drug-induced respiratory disease website: www.pneumotox.com http://www.pneumotox.com/
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]