Simple pulmonary eosinophilia (SPE), also known as Loeffler syndrome, is a rare, temporary (transient) respiratory disorder characterized by the accumulation of eosinophils in the lungs (pulmonary eosinophilia). Eosinophils are a type of white blood cell and are part of the immune system. They are usually produced in response to allergens, inflammation or infection and are particularly active in the respiratory tract. Most cases of SPE are believed to be due to an allergic reaction to drugs and infection (especially parasitic ones). SPE usually ranges in severity from individuals who do not develop any symptoms (outside of eosinophilia) to individuals who develop mild symptoms. In extremely rare cases, more significant complications can occur. Generally, no specific therapy is required as symptoms usually go away spontaneously without treatment.
Simple pulmonary eosinophilia was first described in the medical literature in 1932. It is classified as a form of eosinophilic lung disease, a large group of interstitial lung diseases. SPE is considered a benign, self-limiting disorder.
SPE usually presents as a mild lung disorder characterized by a dry, unproductive cough and a slight fever. Some affected individuals may cough up a mixture of saliva and mucus (sputum). Symptoms usually resolve on their own without treatment (spontaneous resolution) usually within two weeks to a month. In rare cases, symptoms can persist for months especially in the setting of antigen re-exposure.
Additional symptoms can occur in some cases including chest pain, wheezing, shortness of breath (dyspnea), and a rapid breathing rate. Some individuals may complain of a general feeling of poor health (malaise). Inflammation of the mucous membranes of the nose (rhinitis), unintended weight loss and night sweats have also been reported.
According to the medical literature, some individuals with SPE develop acute eosinophilic pneumonia (AEP). AEP is a rare, serious lung disorder that can quickly progress to cause acute respiratory failure. (For more information on AEP, see the related disorders section below).
Generally, SPE is caused by an allergic reaction. A variety of factors including parasitic infection, exposure to certain drugs or exposure to certain fungi have been linked to SPE. In some cases of SPE, the triggering event or cause of SPE is unknown (idiopathic). The exact reason why there is an overproduction and accumulation of eosinophils in the lungs in individuals with SPE is not fully understood.
Most cases are caused by the passage of parasitic larva through the lungs, which result in an allergic reaction. Parasitic worms (helminths) such as nematodes are the most common parasitic cause associated with SPE. The term nematode is a classification (i.e., phylum) of worms characterized by long, round, generally smooth bodies. Nematodes that have been linked to SPE include hookworms and Ascaris lumbricoides, a type of roundworm.
Drugs that have been linked to cases of SPE include nonsteroidal anti-inflammatory drugs (NSAIDs), certain antibiotics, anti-microbials, and anti-seizure medications (anticonvulsants).
Some cases of SPE have been caused by exposure to certain fungi such as Aspergillus fumigatus.
SPE affects males and females in equal numbers. The exact incidence and prevalence of SPE in the general population is unknown. It is the most common form of eosinophilic lung disease. SPE can affect individuals of any age.
A diagnosis of SPE is based upon identification of characteristic symptoms (e.g., eosinophilic pneumonia), a detailed patient history, a thorough clinical evaluation, the absence of other known causes of eosinophilic lung disease, and a variety of specialized tests. A physical examination may reveal wheezing and/or a rattling sound in the lungs (rales). Distinguishing SPE from other, more severe forms of pulmonary eosinophilia is especially important when obtaining a diagnosis.
Clinical Testing and Work-Up
Imaging techniques may be used to help confirm a diagnosis of SPE including chest x-ray or computerized tomography (CT) scanning. Chest x-rays in individuals with SPE generally show white patches or shadows (infiltrates) in the lungs. These infiltrates may disappear, but can reappear in different areas of the lungs. A CT scan may reveal hazy areas (ground-glass opacities) that are not seen on traditional x-rays. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures such as the lungs. A CT scan can also show airspace consolidation, in which the tiny air sacs of the lungs (alveolar) become abnormally filled (as with eosinophils).
A procedure known as bronchoalveolar lavage (BAL) may also be used to help obtain a diagnosis of SPE. During BAL, a narrow tube (bronchoscope) is slid down the windpipe into the lungs and a sterile solution is passed through the tube washing out (lavaging) cells. This fluid is collected and then the tube is removed, allowing the cells to be studied. BAL in individuals with SPE reveals abnormally high levels of eosinophils.
Blood tests may reveal mildly elevated levels of eosinophils and/or serum immunoglobulin E (IgE). A stool examination may reveal the presence of parasites. Analysis of sputum or fluid obtained from pumping the stomach (gastric lavage) may reveal parasitic larvae.
Additional tests may be performed to rule out other causes of pulmonary eosinophilia.
In most cases, no treatment is required and SPE goes away on its own (spontaneous remission). Cases due to active parasitic infection should be treated with appropriate anti-parasitic medications. Drug-induced cases should be treated by stopping the offending medication. In rare cases, corticosteroid therapy may be required and is generally highly effective. In some cases, SPE will recur.
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