Hypersensitivity Pneumonitis | Restrictive Lung Diseases | Pulmonology

Restrictive lung diseases hinder air intake due to restricted lung expansion, likened to a tight rubber band constricting. This results in decreased lung volumes and capacities with normal or increased FEV1/FVC ratios for diagnosis. Severity is determined by Total Lung Capacity (TLC), where lower TLC indicates more severe restriction.

Lung diseases are categorized into extrinsic and intrinsic. Extrinsic issues involve thoracic wall, diaphragm, pleura, or abdomen faults. In contrast, intrinsic problems occur within the interstitial tissue between alveoli like interstitial lung disease or alveolar proteinosis.

Occupations like farmers, carpenters, bird owners, tobacco growers, industrial workers, machine operators are prone to type 4 hypersensitivity reactions. Antigens triggering these reactions can be fungal or bacterial in nature and may come from birds or wood-related chemicals such as moldy hay.

Hypersensitivity pneumonitis includes various subtypes like farmer's lung, bird fanciers lung, chemical workers lung, Millard's lung, cheese washers lung, coffee makers lung. Other examples are tobacco growers'lung and sauna takers'lung.

The four most important subtypes of restrictive lung diseases are hypersensitivity, farmer's lung, bird fanciers or bird keepers lung, and chemical workers lung. Farmer's lung is caused by exposure to fungal antigens like Saccharopolyspora rectivirgula found in moldy hay. Bird keepers' lungs result from exposure to avian proteins present in bird feathers and droppings such as those from parakeets and pigeons.

Classification of Hypersensitivity Pneumonitis Hypersensitivity pneumonitis is classified into acute, subacute, and chronic forms based on the duration of exposure to the antigen. In acute cases, symptoms like fever, chills, malaise develop within hours after exposure and resolve quickly once the patient avoids contact with the antigen.

Subacute Hypersensitivity Pneumonitis Subacute hypersensitivity pneumonitis occurs with ongoing gradual exposure to the antigen. It is characterized by a less intense presentation compared to acute cases but takes longer to resolve due to prolonged contact with the triggering agent.

Chronic Hypersensitivity Pneumonitis Chronic hypersensitivity pneumonitis results from continuous long-term exposure to an antigen. The symptoms progress gradually over time leading to persistent dyspnea, coughing, and fatigue. 'Chronic' indicates that it requires a significant period for manifestation and resolution.

Complications of hypersensitivity pneumonitis can lead to irreversible lung fibrosis, respiratory failure, and hypoxemia. Hypoxemia is defined as decreased partial pressure of oxygen in the blood that does not resolve even after treatment.

Understanding Lung Disease Diagnosis Diagnosis involves exposing a former to moldy hay antigen to check for symptoms development, indicating conditions like allergic bronchopulmonary aspergillosis. High-resolution CT scans reveal ground glass opacity and subpleural honeycombing in restrictive lung diseases. Bronchiectasis occurs due to fibrosis causing traction on bronchioles, leading to complications like act Asia.

Managing Hypersensitivity Pneumonitis Hypersensitivity pneumonitis, such as farmer's lung, results from chronic exposure to antigens like moldy hay. Treatment includes antigen avoidance but can be challenging for individuals reliant on agricultural work. Glucocorticoids may be necessary if avoiding the antigen does not alleviate symptoms.

Lung transplant is considered a last resort for severe cases, such as idiopathic pulmonary fibrosis and hypersensitivity pneumonitis. Idiopathic conditions indicate unknown pathology, while hypersensitivity pneumonitis has an identifiable trigger like Antron exposure. Patients with occupational exposures may present with waxing and waning symptoms based on antigen contact, showing granulomas in lung biopsies.

Base enosis is an organic dust-induced interstitial lung disease, not immune-related like hypersensitivity pneumonitis. Patients exposed to hemp or cotton dust may experience knee and chest tightness with decreased FEV1 on Mondays due to work exposure. The condition is characterized by symptoms starting at the beginning of the week and disappearing on weekends.

Cyberflares disease is distinct from hypersensitivity pneumonitis and results from prolonged exposure to nitrogen dioxide. It triggers a type 1 immediate hypersensitivity reaction, leading to symptoms like dyspnea and wheezing. Unlike hypersensitivity pneumonitis, cyberflares do not involve IgE or an allergic response.

Review of MERS, a long hyper 17m nights extrinsic allergic alveoli antigen causing restrictive lung disease. Not type 1 hypersensitivity or related to IgG antibodies; T helper lymphocytes lead to lung restriction or obstruction. Farmers' lung can be type 3 hypersensitivity, chronic cases may be type 4 due to thermophilic act II.

Using masks can help minimize exposure to hypersensitivity reactions, although it does not completely eliminate the issue. Steroids are recommended if initial treatments fail.

Siloam Father's Lung is linked to nitrogen dioxide exposure from grain storage silos, not hypersensitivity pneumonitis. The condition can lead to chronic bronchitis and obstructive lung diseases like COPD. It causes alveolar damage and bronchiolitis obliterans, treated with immediate steroid therapy.

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