Eosinophilic Pneumonia: Symptoms, Types, Causes and Treatment

Eosinophilic pneumonia is a rare, complex lung disorder marked by the accumulation of eosinophils—a type of white blood cell—in lung tissues and airspaces. This condition can present acutely or develop gradually, and while it often responds well to treatment, it can sometimes be severe or even life-threatening. Understanding its symptoms, types, underlying causes, and treatment options is crucial for early recognition and effective management.

Symptoms of Eosinophilic Pneumonia

Eosinophilic pneumonia can manifest with a wide range of symptoms that often mimic other respiratory illnesses, making diagnosis challenging. Recognizing the characteristic features and subtle differences between acute and chronic forms is essential for both patients and healthcare providers.

Onset	Key Symptoms	Disease Form	Sources
Acute	Fever, cough, dyspnea, myalgias, rapid progression, hypoxemia	Acute (AEP)	1, 4, 5, 10, 11
Chronic	Cough, dyspnea, fever, weight loss, night sweats, gradual onset	Chronic (CEP)	2, 3, 5, 10
Severe	Respiratory failure, need for ventilation	Mostly AEP	1, 4, 5, 11
Systemic	Asthma, allergic symptoms	Often with CEP	2, 3, 5

Table 1: Key Symptoms

Acute vs. Chronic Presentations

• Acute Eosinophilic Pneumonia (AEP):

  • Onset is rapid—symptoms develop over days to a few weeks.
  • High fever, cough, shortness of breath (dyspnea), and muscle aches are common.
  • Severe cases may progress to respiratory failure, requiring hospitalization and mechanical ventilation 1, 4, 5, 10, 11.
  • Hypoxemia (low blood oxygen) is a hallmark and can become life-threatening quickly.

• Chronic Eosinophilic Pneumonia (CEP):

  • Symptoms develop more slowly, often over weeks to months.
  • Persistent cough, increasing shortness of breath, fever, weight loss, and sometimes night sweats are typical 2, 3, 5, 10.
  • Many patients have a history of asthma or atopic (allergic) conditions.
  • Relapses are common, especially when tapering or stopping treatment 3.

Notable Clinical Features

• Respiratory Symptoms:

  • Both AEP and CEP present with cough and dyspnea.
  • CEP is more likely to include wheezing, especially in patients with asthma 3, 5.

• Systemic Symptoms:

  • Fever is more prominent and acute in AEP, while weight loss and night sweats are more common in CEP 2, 3.
  • Muscle aches and general malaise are frequently reported in the acute phase 4.

• Severity Spectrum:

  • Mild cases may be almost asymptomatic or present only with subtle infiltrates on imaging 8.
  • Severe AEP can result in acute respiratory distress syndrome (ARDS), requiring emergency care 1, 4, 11.

Types of Eosinophilic Pneumonia

Eosinophilic pneumonia is not a single disease but a spectrum of disorders, primarily divided into acute and chronic forms, with additional subtypes based on cause and presentation.

Type	Distinguishing Features	Relapse Tendency	Sources
Acute (AEP)	Rapid onset, severe hypoxemia, often young adults, usually no prior asthma	Rare	1, 2, 4, 5, 7, 10, 11
Chronic (CEP)	Slow onset, persistent symptoms, asthma/allergy history common	Common	2, 3, 5, 7, 10, 12, 13
Secondary	Linked to drugs, toxins, infections	Variable	6, 7, 8, 9
Syndromic	Associated with systemic diseases (e.g., Churg-Strauss, HES)	Depends on syndrome	6, 8

Table 2: Types of Eosinophilic Pneumonia

Acute Eosinophilic Pneumonia (AEP)

• Typically affects younger adults without a prior history of asthma or allergies 1, 4.
• Presents acutely, often within days of exposure to a trigger (e.g., new medications, smoking, environmental change) 1, 7, 9, 11.
• Rapidly progressive and may lead to respiratory failure, but responds quickly to corticosteroids 1, 4, 11.
• Relapses are rare after successful treatment 10.

Chronic Eosinophilic Pneumonia (CEP)

• More common in middle-aged women and individuals with asthma or allergic conditions 2, 3.
• Symptoms progress over weeks to months.
• Radiographically, shows characteristic peripheral or “photographic negative” pulmonary infiltrates 2, 3.
• High relapse rates, especially when tapering or discontinuing corticosteroids 3, 12, 13.
• May become corticosteroid-dependent in some patients.

Secondary and Syndromic Forms

• Secondary Eosinophilic Pneumonia: Caused by drugs (e.g., antibiotics, NSAIDs), environmental toxins (cigarette smoke, illicit drugs), radiation, or infections (especially parasitic) 6, 7, 8, 9.
• Syndromic Eosinophilic Pneumonia: Part of systemic disorders like Churg-Strauss syndrome (now called eosinophilic granulomatosis with polyangiitis) and hypereosinophilic syndrome (HES), often with extrapulmonary symptoms 6, 8.

Causes of Eosinophilic Pneumonia

Understanding the causes of eosinophilic pneumonia is critical for prevention and management, as the condition may result from a wide array of triggers—many of which are identifiable and avoidable.

Cause Category	Examples	Mechanism/Trigger	Sources
Idiopathic	AEP, CEP	Unknown, immune-mediated	2, 3, 5, 10
Drugs	Antibiotics, NSAIDs, daptomycin	Hypersensitivity reaction	7, 9, 10
Infections	Parasites (Ascaris, Strongyloides, etc.)	Direct invasion, immune response	6, 8, 9
Toxins	Cigarette smoke, illicit drugs, radiation	Inhalational injury, immune trigger	7, 9
Systemic Disease	Churg-Strauss, HES	Multi-organ eosinophilia	6, 8

Table 3: Causes and Triggers

Idiopathic Eosinophilic Pneumonia

• The majority of cases are considered idiopathic, meaning no clear cause can be identified 2, 3, 5, 10.
• Both AEP and CEP can be idiopathic, often suspected to involve immune system dysregulation.

Drug-Induced Eosinophilic Pneumonia

• Numerous medications have been implicated, including antibiotics, NSAIDs, and chemotherapeutic agents 7, 9, 10.
• Daptomycin is a notable cause of drug-induced cases 7.
• The diagnosis is often supported by a temporal relationship between drug initiation and symptom onset, and resolution after stopping the medication 9.

Infection-Related Eosinophilic Pneumonia

• Parasitic infections are a well-known cause, especially in endemic regions or with relevant travel history 6, 8.
  • Common parasites include Ascaris, hookworms, Strongyloides, Paragonimus, filariasis, and Toxocara 6.
• Fungal infections (e.g., allergic bronchopulmonary aspergillosis) can also trigger eosinophilic infiltration 6.

Toxins and Environmental Exposures

• Inhalation of cigarette smoke (including new smokers or those who recently increased smoking), illicit drugs, and occupational exposures can induce AEP 7, 9, 11.
• Radiation therapy, notably for breast cancer, has also been associated with eosinophilic pneumonia 9.

Systemic and Syndromic Causes

• Eosinophilic pneumonia can be a manifestation of systemic diseases such as:
  • Churg-Strauss syndrome/eosinophilic granulomatosis with polyangiitis, often with extrathoracic involvement.
  • Hypereosinophilic syndrome (HES), where eosinophilia affects multiple organs, including the heart, which dominates prognosis 6, 8.

Treatment of Eosinophilic Pneumonia

Treatment of eosinophilic pneumonia is generally effective, especially when initiated promptly. The mainstay is corticosteroids, but management must be tailored to the underlying type and cause.

Treatment	Indication	Outcome/Notes	Sources
Corticosteroids	AEP, CEP, severe cases	Dramatic, rapid response	1, 3, 4, 8, 10, 11, 12
Drug/Exposure Cessation	Secondary EP	Often sufficient alone	7, 9
Antiparasitics	Parasitic infection	Targeted therapy	6, 8
Immunosuppressants	Churg-Strauss, HES, severe/relapsing cases	Added to steroids if needed	8, 13
Biologics (e.g., mepolizumab)	Relapsing CEP	Reduces relapses, steroid use	13

Table 4: Treatment Approaches

Corticosteroid Therapy

• Acute Eosinophilic Pneumonia (AEP):

  • High-dose corticosteroids are the first-line therapy 1, 4, 11.
  • Rapid clinical and radiographic improvement is typical, with resolution of symptoms in days 4, 11.
  • Short courses (as little as 2 weeks) appear to be effective, even in severe cases 11.
  • Relapse is rare after discontinuation 10, 11.

• Chronic Eosinophilic Pneumonia (CEP):

  • Also responds dramatically to corticosteroids 3, 12.
  • However, relapse is common—over half of patients may experience recurrence after stopping therapy 3, 12.
  • Both 3-month and 6-month steroid regimens show similar relapse rates; resuming steroids is typically effective in controlling recurrences 12.
  • Long-term, low-dose maintenance therapy may be required in frequent relapsers 3.

Addressing Secondary Causes

• Discontinuation of the offending drug or removal from exposure (e.g., cigarette smoke, occupational fumes) is essential in secondary eosinophilic pneumonia 7, 9.
• Most cases resolve after cessation of exposure, but corticosteroids are used if respiratory failure is present 7, 9.

Treatment of Infectious and Syndromic Forms

• Parasitic and fungal infections require targeted antiparasitic or antifungal agents 6, 8.
• Churg-Strauss syndrome and HES:
  • Require systemic corticosteroids, often with additional immunosuppressive therapy in severe or relapsing cases 8.
  • Newer treatments, such as imatinib for the myeloproliferative variant of HES, show promise 8.

Biologic Therapies

• Mepolizumab, an anti-IL-5 antibody, has shown efficacy in reducing relapses and steroid use in relapsing CEP, offering a steroid-sparing option 13.

Conclusion

Eosinophilic pneumonia is a diverse group of lung disorders that, despite their rarity, pose significant diagnostic and management challenges. Early recognition and intervention are essential due to the rapid progression seen in some forms and the high relapse rates in others.

Key Takeaways:

• Symptoms vary by type: Acute forms present rapidly with severe respiratory symptoms, while chronic forms are more insidious with systemic features.
• Main types: Acute (AEP) and chronic (CEP) forms are the primary categories, with additional secondary and syndromic variants.
• Causes: Most cases are idiopathic, but drugs, infections, toxins, and systemic diseases can all play a role.
• Treatment: Corticosteroids are highly effective, but relapse is common in chronic forms; new biologic therapies are emerging for refractory cases.
• Prevention: Identifying and removing offending triggers is crucial in secondary cases.

Ongoing research continues to refine our understanding and treatment of eosinophilic pneumonia, offering hope for improved outcomes and quality of life for affected individuals.