- • Eosinophilic pneumonia is defined by the presence
of pulmonary infiltrates and the demonstration of either peripheral
blood eosinophilia, bronchoalveolar lavage fluid eosinophilia, or
lung tissue eosinophilia.
- • Eosinophilic pneumonia is classified as acute or
- • Acute eosinophilic pneumonia presents with the
rapid onset of lower respiratory tract symptoms, often culminating
in acute respiratory failure.
- • Chronic eosinophilic pneumonia has a subacute to
chronic presentation associated with systemic symptoms and peripheral
- • Drug toxicity can cause both acute eosinophilic
pneumonia and chronic eosinophilic pneumonia and should be ruled
out in all cases.
The eosinophilic pneumonias represent a heterogeneous group of
diseases that shares the common feature of eosinophilic infiltration
of lung tissue resulting in an airspace pattern on chest radiograph.
Generally, the eosinophilia is defined by either: (1) pulmonary
infiltrates with peripheral blood eosinophilia, (2) tissue biopsy
of the lungs, or (3) bronchoalveolar lavage. Traditionally, eosinophilic
pneumonia is divided into acute and chronic forms based on the clinical presentation
and course. Acute eosinophilic pneumonia generally occurs in previously
healthy individuals and represents a rapidly progressive disease
that often culminates in acute respiratory failure. Corticosteroid
therapy is very effective and relapse is extremely rare. In contrast,
chronic eosinophilic pneumonia presents with a slower onset of symptoms,
often in persons with a prior history of asthma or sinusitis. Corticosteroids
control the disease but relapses off therapy are common. Careful
attention in the history and physical examination should be given
to identifying secondary causes of eosinophilic pneumonia such as
Acute eosinophilic pneumonia is a rapidly progressive disease
generally seen in healthy adults. There is no gender predilection.
An association with the acquired immunodeficiency syndrome has been
There is no known cause of acute eosinophilic pneumonia. It has
been speculated that it represents an allergic response to exogenous
stimuli. Bronchoalveolar lavage, which samples the alveolar air spaces,
has revealed an increased number of eosinophils and an increased
concentration of interleukin-5, an eosinophil chemoattractant, in
patients with acute eosinophilic pneumonia. Lung biopsy reveals
diffuse infiltration of alveolar spaces by eosinophils and alveolar
macrophages, accompanied by a proteinaceous exudate, hyaline membranes,
and interstitial expansion by eosinophils. In contrast to chronic
eosinophilic pneumonia, the alveolar exudate and hyaline membranes
imply an acute airspace injury and microabscesses and focal necrosis
are not present.
Acute eosinophilic pneumonia is characterized initially by flu-like
symptoms including fever, malaise, myalgias, and cough. Shortness
of breath develops rapidly over 1 to 5 days with most patients seeking
medical attention within the first week. Physical examination is
notable for fever, tachycardia, hypoxia, and crackles on auscultation.
Initially chest radiographs may show predominantly an interstitial
pattern that rapidly progresses to diffuse, airspace disease. Small
pleural effusions have been noted. Laboratory studies are notable
for the absence of peripheral blood eosinophilia.
The diagnostic criteria for ...