(See also Overview of Eosinophilic Pulmonary Diseases Overview of Eosinophilic Pulmonary Diseases Eosinophilic pulmonary diseases are a heterogeneous group of disorders characterized by the accumulation of eosinophils in alveolar spaces, the interstitium, or both. Peripheral blood eosinophilia... read more .)
In contrast to chronic eosinophilic pneumonia Chronic Eosinophilic Pneumonia Chronic eosinophilic pneumonia (CEP) is a disorder of unknown etiology characterized by an abnormal, chronic accumulation of eosinophils in the lung. (See also Overview of Eosinophilic Pulmonary... read more , acute eosinophilic pneumonia is an acute illness that does not usually recur. Incidence and prevalence are unknown. Acute eosinophilic pneumonia can occur at any age but most often affects patients between 20 and 40 years, with a male-to-female ratio of 2:1.
The cause is unknown, but acute eosinophilic pneumonia may be an acute hypersensitivity reaction Drug Hypersensitivity Drug hypersensitivity is an immune-mediated reaction to a drug. Symptoms range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is clinical; skin testing is occasionally... read more to an unidentified inhaled antigen in an otherwise healthy person. Cigarette or other smoke exposure may be involved.
Symptoms and Signs of Acute Eosinophilic Pneumonia
Acute eosinophilic pneumonia causes an acute febrile illness of short duration (usually < 7 days). Symptoms are nonproductive cough, dyspnea, malaise, myalgias, night sweats, and pleuritic chest pain.
Signs include tachypnea, fever (often > 38.5° C), and bibasilar inspiratory crackles and, occasionally, rhonchi on forced exhalation.
Patients with acute eosinophilic pneumonia frequently present with acute respiratory failure Overview of Respiratory Failure Acute respiratory failure is a life-threatening impairment of oxygenation, carbon dioxide elimination, or both. Respiratory failure may occur because of impaired gas exchange, decreased ventilation... read more requiring mechanical ventilation. Rarely, distributive (hyperdynamic) shock Distributive shock Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes... read more can occur.
Diagnosis of Acute Eosinophilic Pneumonia
High-resolution CT (HRCT)
Usually complete blood count (CBC), pleural fluid analysis, and pulmonary function testing
Bronchoscopy for lavage and, sometimes, biopsy
The diagnosis of acute eosinophilic pneumonia is suspected in patients with symptoms of acute pneumonia that progress to respiratory failure and do not respond to antibiotics. Diagnosis is based on findings from routine testing and is confirmed by bronchoscopy.
Acute eosinophilic pneumonia is a diagnosis of exclusion and requires the absence of known causes of eosinophilic pneumonia (eg, drug- and toxin-induced, helminthic and fungal infection–related, eosinophilic granulomatosis with polyangiitis Eosinophilic Granulomatosis with Polyangiitis (EGPA) Eosinophilic granulomatosis with polyangiitis is a systemic small- and medium-vessel necrotizing vasculitis, characterized by extravascular granulomas, eosinophilia, and tissue infiltration... read more , hypereosinophilic syndrome Hypereosinophilic Syndrome Hypereosinophilic syndrome is a condition characterized by peripheral blood eosinophilia with manifestations of organ system involvement or dysfunction directly related to eosinophilia in the... read more , tumors).
The CBC often fails to demonstrate markedly elevated eosinophil counts, unlike in chronic eosinophilic pneumonia Chronic Eosinophilic Pneumonia Chronic eosinophilic pneumonia (CEP) is a disorder of unknown etiology characterized by an abnormal, chronic accumulation of eosinophils in the lung. (See also Overview of Eosinophilic Pulmonary... read more . Erythrocyte sedimentation rate (ESR) and IgE levels are high but are nonspecific.
The chest x-ray initially may show only subtle reticular or ground-glass opacities, often with Kerley B lines. Isolated alveolar (about 25% of cases) or reticular (about 25% of cases) opacities may also be observed. Unlike in chronic eosinophilic pneumonia, in acute eosinophilic pneumonia opacities are not characteristically localized to the lung periphery. Small pleural effusions Pleural Effusion Pleural effusions are accumulations of fluid within the pleural space. They have multiple causes and usually are classified as transudates or exudates. Detection is by physical examination and... read more occur in two thirds of patients and are frequently bilateral.
HRCT is always abnormal with bilateral, random, patchy ground-glass or reticular opacities.
Pleural fluid examination shows marked eosinophilia and high pH.
Pulmonary function tests Overview of Tests of Pulmonary Function Pulmonary function tests provide measures of airflow, lung volumes, gas exchange, response to bronchodilators, and respiratory muscle function. Basic pulmonary function tests available in the... read more often show a restrictive process with reduced diffusing capacity for carbon monoxide (DLCO).
Bronchoscopy Bronchoscopy Bronchoscopy is the introduction of an endoscope into the airways. Flexible fiberoptic bronchoscopy is used for virtually all diagnostic, and most therapeutic, indications. Flexible bronchoscopes... read more should be done for lavage and, occasionally, biopsy. Bronchoalveolar lavage fluid often shows a high number and percentage (> 25%) of eosinophils. The most common histopathologic features on biopsy include eosinophilic infiltration with acute and organizing diffuse alveolar damage, but few patients have undergone lung biopsy.
Treatment of Acute Eosinophilic Pneumonia
Some patients with acute eosinophilic pneumonia improve spontaneously. Most are treated with prednisone 40 to 60 mg orally once a day. In patients with respiratory failure, methylprednisolone 60 to 125 mg IV every 6 hours is preferred.
The prognosis of acute eosinophilic pneumonia is usually good; response to corticosteroids and complete recovery are common. Pleural effusions resolve more slowly than parenchymal opacities.