Bird Fancier Lung

Bird fancier lung (pigeon breeder's lung, bird related hypersensitivity pneumonitis) is hypersensitivity pneumonitis caused by inhalation of avian proteins from feathers, droppings and serum of pigeons, budgerigars, parrots, cockatiels, chickens and also feather bedding (duvets, pillows).

• Most common form of HP in many countries; prevalence 5 to 20% of exposed pigeon breeders.
• Pathogenesis: avian IgA, droppings antigens; immune complex and T cell mediated.
• Forms: acute, subacute, chronic (fibrotic); chronic exposure to low levels (domestic birds, down) can cause insidious fibrosis resembling IPF, with higher mortality in fibrosis.
• Exposure may be hidden: nearby bird droppings, feather duvets, bird in neighbour's loft.

• Acute: flu like illness 4 to 8 hours after contact: fever, chills, cough, dyspnoea, myalgia.
• Subacute: progressive cough, breathlessness, fatigue, weight loss.
• Chronic: exertional dyspnoea, clubbing, crackles; weight loss.
• Symptoms improve away from birds (weekends, holidays).

• Exposure history (birds at home or work, feather bedding, damp environments).
• Serum IgG precipitins against avian antigens (pigeon serum, droppings).
• HRCT: ground glass, centrilobular nodules, mosaic attenuation, air trapping; fibrosis (honeycombing, traction bronchiectasis) with upper or mid zone predominance in chronic.
• Pulmonary function: restriction, reduced DLCO; exercise desaturation.
• Bronchoalveolar lavage lymphocytosis; biopsy if uncertain.
• Specific inhalational challenge in expert centres.

• Complete antigen avoidance: remove or rehome birds, avoid feather bedding, clean environment, thoroughly dry/clean ventilation and humidifier systems; occupational change. Partial avoidance is often insufficient.
• Prednisolone 0.5 mg/kg (30 to 40 mg) daily for 4 to 6 weeks then taper over 3 to 6 months for symptomatic or physiologically impaired disease or severe acute episodes.
• Steroid sparing agents for chronic or relapsing: mycophenolate mofetil 1 to 1.5 g twice daily, azathioprine 1 to 2 mg/kg, rituximab for refractory cases.
• Progressive fibrotic disease: nintedanib 150 mg twice daily.
• Supportive: oxygen, vaccinations, pulmonary rehabilitation.
• Follow up with symptoms, spirometry, DLCO, HRCT; early disease reversible, fibrosis mostly irreversible.
• Lung transplantation for end stage disease.