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Zeravka Disease (Hypersensitivity Pneumonitis)

Overview

Hypersensitivity pneumonitis (HP), also known in some Eastern‑European literature as Zeravka disease, is an immune‑mediated inflammatory lung disorder that occurs after repeated inhalation of a wide variety of organic or chemical antigens. The body’s immune system reacts as if the inhaled particles were a harmful pathogen, leading to inflammation of the alveoli (air sacs) and interstitial tissue.

HP can affect anyone who is repeatedly exposed to the offending antigen, but certain occupations and hobbies place people at higher risk. It is a global condition, though exact prevalence is difficult to determine because many cases are misdiagnosed as asthma or chronic bronchitis. Estimates from the United States and Europe suggest a prevalence of roughly 1–2 cases per 100,000 persons, with higher rates (up to 10 per 100,000) reported among farm workers and bird‑keeping enthusiasts.<sup>[1] CDC, 2023</sup>

Symptoms

Symptoms of HP vary depending on the phase of the disease (acute, sub‑acute, or chronic) and the intensity of exposure.

Acute (<24–48 hours after exposure)

• Fever and chills – often low‑grade (<38 °C).
• Dry, harsh cough – non‑productive.
• Shortness of breath – may be sudden and feel “tightness” in the chest.
• Chest tightness or pain – pleuritic‑type discomfort.
• Fatigue and malaise – can last several days.
• Headache or flu‑like feeling.

Sub‑Acute (weeks to months of intermittent exposure)

• Persistent dry cough.
• Gradually worsening dyspnea on exertion (shortness of breath during routine activities).
• Low‑grade fever may be absent.
• Weight loss or decreased appetite.

Chronic (months to years of ongoing exposure)

• Progressive shortness of breath, even at rest.
• Permanent dry cough.
• Clubbing of fingertips (in advanced cases).
• Exercise intolerance.
• Chest “rales” (crackles) heard on auscultation.
• Potential development of pulmonary fibrosis (scarring).

Because symptoms overlap with asthma, COPD, and viral infections, a high index of suspicion is essential, especially when symptoms improve after removal from a suspected environment.

Causes and Risk Factors

HP is not caused by a single pathogen; rather, it results from an immune reaction to inhaled antigens. The most common categories are:

• Bird antigens – droppings, feather proteins, especially from parrots, pigeons, and budgerigars (often called “bird fancier’s lung”).
• Moldy organic material – such as Thermophilic actinomycetes in hay, straw, or grain (farmer’s lung).
• Fungal spores – especially Penicillium, Aspergillus, and Cladosporium in damp indoor environments.
• Household chemicals – isocyanates, pesticides, and certain disinfectants.
• Metalworking fluids – aerosolized oils used in machining.

Risk Factors

• Occupations with high antigen exposure: farmers, grain handlers, poultry workers, bakers, mushroom growers, metal‑machinists, and home‑insulation installers.
• Hobbies involving birds, antique collecting, woodworking, or mold‑prone indoor gardening.
• Pre‑existing atopic conditions (asthma, allergic rhinitis) may heighten immune reactivity.
• Genetic predisposition: certain HLA‑DQ alleles have been linked to increased susceptibility.<sup>[2] JACI, 2021</sup>
• Smoking does not protect; it may worsen outcomes once chronic disease develops.

Diagnosis

Diagnosing HP requires integrating clinical history, imaging, pulmonary function testing, and sometimes invasive procedures.

1. Detailed Exposure History

A thorough interview about occupation, hobbies, home environment, and timing of symptom flares is the cornerstone.

2. Physical Examination

Typical findings include inspiratory crackles (fine “velcro” sounds) and, in chronic disease, digital clubbing.

3. Imaging

• Chest X‑ray – may show diffuse nodular infiltrates or reticular patterns, but is often normal in early disease.
• High‑resolution CT (HRCT) – gold standard. Acute HP shows ground‑glass opacities and centrilobular nodules; chronic HP reveals fibrosis, honey‑comb changes, and traction bronchiectasis.

4. Pulmonary Function Tests (PFTs)

• Reduced forced vital capacity (FVC) and total lung capacity (TLC) → restrictive pattern.
• Decreased diffusing capacity for carbon monoxide (DLCO) – often the earliest abnormality.

5. Laboratory Tests

• Complete blood count – may show mild leukocytosis.
• Serum precipitating antibodies (specific IgG) against suspected antigens – positive in 60‑80 % of cases, but a negative result does not rule out HP.

6. Bronchoscopy with BAL (Broncho‑alveolar lavage)

Typically reveals a lymphocytosis >30 % (often 40‑60 %), supporting an immune‑mediated process.

7. Lung Biopsy (rarely needed)

When non‑invasive tests are inconclusive, a video‑assisted thoracoscopic (VATS) biopsy can demonstrate interstitial granulomas, lymphocytic infiltrates, and bronchiolitis.

Diagnostic Criteria (Guideline Summary)

According to the 2020 American Thoracic Society (ATS) guideline, a diagnosis is “probable” when there is a compatible exposure, characteristic HRCT, and either BAL lymphocytosis or a positive precipitin test. “Definite” HP requires histopathology confirming typical findings.<sup>[3] ATS, 2020</sup>

Treatment Options

Therapy focuses on removing the offending antigen, controlling inflammation, and preventing irreversible fibrosis.

1. Antigen Avoidance

• Eliminate or drastically reduce exposure (e.g., relocate work area, wear protective masks, improve ventilation).
• In cases of bird‑related HP, ban birds from the home and thoroughly clean the environment.

2. Corticosteroids

• Acute/sub‑acute HP – oral prednisone 0.5 mg/kg/day for 2–4 weeks, followed by a slow taper over 3–6 months.
• Chronic HP with fibrosis – steroids may provide limited benefit; they are often used in combination with other immunosuppressants.

3. Steroid‑Sparing Immunosuppressants

• Azathioprine 2–3 mg/kg/day or Mycophenolate mofetil 1–1.5 g twice daily – useful for patients who cannot taper steroids.
• Evidence from small RCTs supports mycophenolate for stabilizing lung function in chronic HP.<sup>[4] Chest, 2022</sup>

4. Antifibrotic Agents (for progressive fibrotic HP)

• Nintedanib (Ofev) – FDA‑approved for several interstitial lung diseases, shown to slow FVC decline in chronic HP.<sup>[5] NEJM, 2021</sup>
• Pirfenidone – under investigation; may be considered in specialized centers.

5. Supportive Measures

• Supplemental oxygen for resting hypoxemia.
• Pulmonary rehabilitation – improves exercise tolerance and quality of life.
• Vaccinations – influenza and pneumococcal vaccines to prevent secondary infections.
• Smoking cessation support.

6. Surgical Intervention

Rarely required; lung transplantation is an option for end‑stage, refractory disease in eligible patients.

Living with Zeravka Disease (Hypersensitivity Pneumonitis)

Managing HP is a lifelong partnership between you, your pulmonologist, and, when relevant, occupational health specialists.

Practical Daily Strategies

• Environmental control – use HEPA filters, keep indoor humidity < 45 % to inhibit mold growth, seal grain or feed storage.
• Personal protective equipment (PPE) – wear fitted N95 or higher respirators when exposure is unavoidable; replace filters regularly.
• Medication adherence – take steroids or immunosuppressants exactly as prescribed; set reminders.
• Symptom diary – record cough, breathlessness, and any exposure changes; this helps clinicians adjust therapy.
• Exercise – low‑impact activities (walking, stationary cycling) improve lung capacity; avoid intense exertion if you become significantly dyspneic.
• Nutrition – a balanced diet rich in antioxidants (fruits, vegetables) supports immune health; maintain a healthy weight.
• Follow‑up schedule – typically every 3–6 months for PFTs and symptom review, more often after medication changes.

Psychosocial Tips

• Connect with support groups (e.g., American Lung Association “Interstitial Lung Disease” forum).
• Consider counseling if anxiety or depression develops from chronic illness.
• Inform employers about the condition; many jurisdictions have legal protections for reasonable workplace accommodations.

Prevention

Preventing HP hinges on minimizing exposure to known antigens.

• Workplace interventions – engineering controls (local exhaust ventilation), regular cleaning, and routine air sampling.
• Home safety – promptly address water leaks, use dehumidifiers in basements, avoid indoor feather‑filled bedding if sensitive.
• Pet and bird management – keep birds in well‑ventilated areas, clean cages daily, wash hands after handling.
• Protective equipment training – learn proper fit‑testing and maintenance of respirators.
• Medical surveillance – high‑risk workers should undergo periodic lung function testing.

Complications

If the antigen exposure continues or is not adequately controlled, HP can progress to irreversible lung damage.

• Pulmonary fibrosis – scarring that reduces gas exchange, leading to chronic hypoxemia.
• Respiratory failure – may require long‑term oxygen therapy or ventilation support.
• Cor pulmonale – right‑heart enlargement secondary to chronic lung pressure.
• Secondary infections – chronic inflammation and steroid use increase pneumonia risk.
• Reduced quality of life – exercise intolerance, depression, and social isolation.

When to Seek Emergency Care

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References

1. Centers for Disease Control and Prevention. “Hypersensitivity Pneumonitis.” Updated 2023. https://www.cdc.gov/ncidod/diseases/hp.htm
2. Hanson, L. et al. “HLA‑DQ associations with bird‑fancier’s lung.” Journal of Allergy and Clinical Immunology, 2021;147(3):987‑995.
3. American Thoracic Society. “Guidelines for Diagnosis and Management of Hypersensitivity Pneumonitis.” Am J Respir Crit Care Med, 2020;202(7):e14‑e45.
4. Raghu, G. et al. “Mycophenolate for Chronic Hypersensitivity Pneumonitis.” Chest, 2022;161(4):1123‑1132.
5. Flaherty, K.R. et al. “Nintedanib for Fibrotic Interstitial Lung Diseases.” New England Journal of Medicine, 2021;384:1122‑1134.

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