Hypersensitivity Pneumonitis: Causes, Symptoms and Management

Hypersensitivity pneumonitis (HP) is a complex lung condition that occurs when your lungs develop an immune response after repeated exposure to certain substances. Also known as extrinsic allergic alveolitis, hypersensitivity pneumonitis can cause inflammation and damage to the lung tissue, leading to breathing difficulties and other respiratory symptoms. In this article, we'll explore the causes, symptoms, diagnosis, and treatment options for hypersensitivity pneumonitis, helping you better understand and manage this condition. 

What is hypersensitivity pneumonitis?  

Hypersensitivity pneumonitis is an inflammatory lung disease triggered by an allergic reaction to inhaled organic dust, moulds, or chemicals. When you repeatedly breathe in these substances, your immune system may become sensitised and mount an exaggerated response, causing inflammation in the airways and lung tissue. 

What is the difference between hypersensitivity pneumonitis and other allergies? 

Unlike common allergies that involve immediate (Type I) hypersensitivity reactions, hypersensitivity pneumonitis is characterised by delayed (Type III and IV) hypersensitivity reactions. These reactions involve immune complexes and T-cell-mediated responses, resulting in a more severe and prolonged inflammatory process in the lungs. 

Who does hypersensitivity pneumonitis affect?  

Hypersensitivity pneumonitis primarily affects individuals with repeated exposure to specific antigens, often due to their occupations or hobbies. Some common risk groups include: 

• Farmers exposed to mouldy hay or grain 

• Bird breeders and pet owners exposed to bird droppings or feathers 

• Workers in industries with exposure to wood dust, chemicals, or moulds 

• People living in homes with water damage or poor ventilation 

Is hypersensitivity pneumonitis serious? 

Yes, hypersensitivity pneumonitis can be a serious condition, especially if left untreated. Chronic HP can lead to permanent lung damage, respiratory failure, and a reduced quality of life. 

How does hypersensitivity pneumonitis affect our body? 

When you inhale the triggering substance, your immune system releases inflammatory cells and chemicals that damage the airways and air sacs (alveoli) in your lungs. This inflammation makes the lung tissue thicken and scar, impairing oxygen exchange and causing respiratory symptoms. Over time, the lung damage can become irreversible, leading to chronic breathing problems and reduced lung function. 

What are the symptoms of hypersensitivity pneumonitis?  

The symptoms of hypersensitivity pneumonitis can vary depending on the stage and severity of the condition. Let's look at the symptoms of acute and chronic HP: 

Symptoms of acute hypersensitivity pneumonitis 

Acute HP typically develops within 4-12 hours after antigen exposure and may include: 

1. Fever and chills 
2. Cough 
3. Shortness of breath 
4. Chest tightness or pain 
5. Fatigue 

Symptoms of chronic hypersensitivity pneumonitis 

Chronic HP results from long-term, low-level exposure and may cause: 

• Persistent dry cough 

• Progressive shortness of breath 

• Fatigue and weakness 

• Unintended weight loss 

• Clubbing of fingers or toes 

What does hypersensitivity pneumonitis feel like?  

Living with hypersensitivity pneumonitis can feel like having a persistent flu that doesn't go away. You may experience ongoing fatigue, cough, and increasing difficulty breathing, especially with physical activity. As the condition progresses, you may feel shortness of breath even at rest, impacting your daily life and overall well-being. 

What causes hypersensitivity pneumonitis? 

Hypersensitivity pneumonitis is caused by inhaling specific antigens, such as: 

• Moulds and fungi: Found in hay, grain, or wood. 

• Bacteria: Present in humidifiers or hot tubs. 

• Bird proteins: From droppings or feathers. 

• Chemicals: In paints, plastics, or pesticides. 

• Genetic factors and susceptibility influence HP development. 

What are the types of hypersensitivity? 

Hypersensitivity pneumonitis involves two main types of hypersensitivity reactions: 

1. Type III (immune complex-mediated) reactions, seen in acute HP 
2. Type IV (cell-mediated) reactions, associated with chronic HP 

These delayed hypersensitivity reactions lead to a more complex and persistent inflammatory response compared to immediate allergic reactions. 

How is hypersensitivity pneumonitis diagnosed? 

Diagnosing hypersensitivity pneumonitis can be challenging, as the symptoms often mimic other respiratory conditions. A thorough evaluation by a pulmonologist is essential and may include: 

• Take a detailed exposure history to identify triggers. 

• Conduct a physical exam for respiratory symptoms. 

• Perform chest X-ray/CT scan for lung abnormalities. 

• Use pulmonary function tests for lung capacity. 

• Run blood tests for antibodies or differential diagnosis. 

• Perform BAL to analyse lung fluid. 

• Conduct a lung biopsy if needed. 

What tests will be done to diagnose hypersensitivity pneumonitis? 

To diagnose hypersensitivity pneumonitis, your doctor may recommend: 

• Blood tests: To check for specific antibodies against the triggering antigen 

• Imaging tests: Chest X-ray or high-resolution CT scan to assess lung damage 

• Pulmonary function tests: Spirometry and diffusion capacity to evaluate lung function 

• Bronchoscopy with BAL: To collect lung fluid samples for analysis 

• Lung biopsy: To examine lung tissue for signs of inflammation or fibrosis 

How is hypersensitivity pneumonitis treated? 

The primary treatment for hypersensitivity pneumonitis is avoiding further exposure to the triggering antigen. Your doctor may also recommend: 

• Corticosteroids: Reduce lung inflammation and prevent damage. 

• Immunosuppressants: Suppress overactive immune response in severe cases. 

• Oxygen Therapy: Improve blood oxygen levels when needed. 

• Pulmonary Rehabilitation: Enhance lung function and quality of life. 

What medications/treatments are used for hypersensitivity pneumonitis?  

The main medications used to treat hypersensitivity pneumonitis include corticosteroids (e.g., prednisone) and immunosuppressive drugs (e.g., azathioprine, mycophenolate). Bronchodilators and oxygen therapy may also be used to manage symptoms. 

How soon after treatment for hypersensitivity pneumonitis will we feel better?  

Treatment response for hypersensitivity pneumonitis varies, with acute cases improving quickly, while chronic cases stabilise slowly or may remain irreversible. 

How do you get rid of hypersensitivity pneumonitis?  

The key to managing hypersensitivity pneumonitis involves: 

• Change occupations or hobbies to avoid exposure. 

• Enhance ventilation and control moisture in the environment. 

• Use personal protective equipment like respirators when exposure is unavoidable. 

• Collaborate with your doctor to develop an effective treatment plan. 

How can we prevent hypersensitivity pneumonitis?  

Preventing hypersensitivity pneumonitis involves minimising exposure to potential triggers. Some strategies include: 

• Wearing protective gear (e.g., masks, respirators) in high-risk environments 

• Ensuring proper ventilation and humidity control in homes and workplaces 

• Regularly cleaning and maintaining air conditioning and humidification systems 

• Promptly addressing water damage or mould growth 

What can we expect if we have hypersensitivity pneumonitis? 

If you have hypersensitivity pneumonitis, you can expect to work closely with your healthcare team to identify triggers, manage symptoms, and prevent disease progression. With proper treatment and lifestyle changes, many people with HP can maintain a good quality of life. 

What is the outlook for hypersensitivity pneumonitis? 

The prognosis for hypersensitivity pneumonitis varies by stage; early diagnosis and treatment improve outcomes, but chronic cases may progress despite intervention, potentially leading to permanent lung scarring. 

What are the complications of hypersensitivity pneumonitis?  

If left untreated or poorly managed, hypersensitivity pneumonitis can lead to serious complications, such as: 

• Pulmonary fibrosis (permanent lung scarring) 

• Respiratory failure 

• Pulmonary hypertension 

• Increased risk of infections 

• Reduced quality of life 

What is the life expectancy of someone with hypersensitivity pneumonitis? 

Life expectancy in hypersensitivity pneumonitis depends on disease severity. Early-stage has better outcomes, while advanced fibrosis worsens prognosis. Timely diagnosis and treatment improve survival and quality of life. 

When to see a doctor about hypersensitivity pneumonitis? 

If you experience persistent respiratory symptoms, especially if you have a history of exposure to potential triggers, it's essential to consult a healthcare professional. Early diagnosis and intervention can significantly improve the outcomes of hypersensitivity pneumonitis. 

Conclusion 

Hypersensitivity pneumonitis is a serious lung condition that requires prompt care. Understanding its causes, symptoms, and treatment options is essential for lung health. If you suspect you may have HP, don't hesitate to seek medical advice and consider undergoing diagnostic testing to identify the underlying cause. Metropolis Healthcare offers accurate diagnostics, including at-home sample collection and health check-ups, to support your healthcare journey and prioritise your well-being. Visit their website for services.