Bird fancier's lung (BFL), also known as bird breeder's lung, is a type of

hypersensitivity pneumonitis Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a syndrome caused by the repetitive inhalation of antigens from the environment in susceptible or sensitized people. Common antigens include molds, bacteria, bird dropping ...

. It can cause

shortness of breath Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...

fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...

dry cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three phas ...

, chest pain,

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

and

weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat ( adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...

, fatigue, and progressive

pulmonary fibrosis Pulmonary fibrosis is a condition in which the lungs become scarred over time. Symptoms include shortness of breath, a dry cough, feeling tired, weight loss, and nail clubbing. Complications may include pulmonary hypertension, respiratory failu ...

(the most serious complication). It is triggered by exposure to avian proteins present in the dry dust of

droppings Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

or feathers of a variety of birds. The lungs become

inflamed Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecu ...

, with granuloma formation. It mostly affects people who work with birds or own many birds. BFL is diagnosed based on symptoms, and how these get worse on exposure to avian proteins.

Radiology Radiology ( ) is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiat ...

can show damage to the lungs, which has a characteristic "ground glass" appearance.

Bronchoscopy Bronchoscopy is an endoscopic technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument (bronchoscope) is inserted into the airways, usually through the nose or mouth, or occasionally through a trac ...

shows chronic inflammation, with

biopsies A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a dise ...

showing

lymphocytosis Lymphocytosis is an increase in the number or proportion of lymphocytes in the blood. Absolute lymphocytosis is the condition where there is an increase in the lymphocyte count beyond the normal range while relative lymphocytosis refers to the cond ...

and granulomatous tissue. BFL may be treated with steroids such as

prednisone Prednisone is a glucocorticoid medication mostly used to suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium due to cancer and ad ...

to reduce

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

, and removal of exposure to avian proteins. If pulmonary fibrosis has not occurred, treatments tend to be very effective.

Signs and symptoms

Initial symptoms of BFL include

(dyspnea), and

. These may be worse after sudden exertion or when exposed to temperature change, which can resemble

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

, hyperventilation syndrome or

pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...

. Chest pain (such as a tight chest), chills, crackly chest, and

may also occur. Upon re-exposure to avian proteins, sensitized individuals typically experience symptoms within 4–8 hours. In chronic BFL, symptoms may include

, extreme fatigue, and progressive

. Pulmonary fibrosis is generally the most serious consequence of the disease, as it progressively and irreversibly diminishes the lungs' efficiency over time. As a result, affected individuals may have repeated chest infections and ultimately struggle to breathe.

Complications

Pulmonary fibrosis can get worse over time. This can eventually lead to

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...

, which can be fatal. Diffuse alveolar damage (DAD) can occur with acute

Cause

BFL is caused by an immune response to inhaled

allergen An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies. In technical terms ...

s from birds. This may be the dry dust of

, or feathers. These

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respons ...

s can come from any bird. BFL may be caused by allergens from

pigeons Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...

. Allergens may also come from other birds, including

parakeets A parakeet is any one of many small to medium-sized species of parrot, in multiple genera, that generally has long tail feathers. Etymology and naming The name ''parakeet'' is derived from the French wor''perroquet'' which is reflected in ...

cockatiels The cockatiel (; ''Nymphicus hollandicus''), also known as weiro (also spelt weero), or quarrion, is a medium-sized parrot that is a member of its own branch of the cockatoo family endemic to Australia. They are prized as household pets and comp ...

budgerigars The budgerigar ( ; ''Melopsittacus undulatus''), also known as the common parakeet or shell parakeet, is a small, long-tailed, seed-eating parrot usually nicknamed the budgie ( ), or in American English, the parakeet. Budgies are the only spe ...

parrots Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoide ...

turtle doves ''Streptopelia'' is a genus of birds in the pigeon and dove family Columbidae. These are mainly slim, small to medium-sized species. The upperparts tend to be pale brown and the underparts are often a shade of pink. Many have a characteristic bla ...

turkeys The turkey is a large bird in the genus ''Meleagris'', native to North America. There are two extant turkey species: the wild turkey (''Meleagris gallopavo'') of eastern and central North America and the ocellated turkey (''Meleagris ocellat ...

, chickens, and other birds. Antigens can also be from feathers in

bedding Bedding, also known as bedclothes or bed linen, is the materials laid above the mattress of a bed for hygiene, warmth, protection of the mattress, and decorative effect. Bedding is the removable and washable portion of a human sleeping environm ...

. People who work with birds or own many birds are at risk. Bird hobbyists and pet store workers may also be at risk.

Mechanism

BFL causes inflammation of the

alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...

in the lungs. Avian proteins include

mucin Mucins () are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most animals. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most ...

s and antibodies, which stimulate a significant immune response from the body. The lungs become

, with granuloma formation. It can take many years of exposure to cause BFL, with an average of 1.6 years to cause acute disease, and 16 years to cause chronic disease.

Diagnosis

Symptoms

A definitive diagnosis can be difficult without invasive testing. Extensive exposure to birds, combined with reduced

diffusing capacity Diffusing capacity of the lung (DL) (also known as Transfer factor is another expression for the formerly used diffusing capacity.) measures the transfer of gas from air in the lung, to the red blood cells in lung blood vessels. It is part of a c ...

, are strongly suggestive of BFL. Symptoms worsen upon skin exposure to avian proteins in 85% of patients. Symptoms tend to occur or worsen within 4 – 8 hours after exposure to avian protein. Symptoms almost always worsen upon lung exposure to avian protein, and such tests are often performed in hospital in case symptoms become hard to manage.

Biochemistry

Biochemical results tend to be difficult to pinpoint to BFL, but can support a diagnosis. BFL causes high concentrations of antibodies targeted against avian proteins, although this may also be found in people exposed to avian protein without the disease. These can be detected in a blood test. An inverted CD4+/CD8+ ratio is associated with

Radiology

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

or CT scans usually show physical changes to the lung structure (a "ground glass" appearance or a "mosaic" pattern) as the disease progresses. Mediastinal lymphadenopathy and bronchiectasis may also be seen. Precise distribution and types of tissue damage differ among similar diseases, as does response to treatment with

. Up to 12% of x-rays may show no damage, whilst only 2% of CT scans show no damage.

Endoscopy

Bronchoalveolar lavage typically shows prominent

. This mainly consists of cytotoxic T cells, with an elevated concentration of

mast cell A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...

s. Standard

bronchoscopy Bronchoscopy is an endoscopic technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument (bronchoscope) is inserted into the airways, usually through the nose or mouth, or occasionally through a trac ...

usually shows

chronic inflammation Chronic systemic inflammation (SI) is the result of release of pro-inflammatory cytokines from immune-related cells and the chronic activation of the innate immune system. It can contribute to the development or progression of certain conditions ...

of lung tissue, and granulomas with poorly-defined margins.

Lung biopsy A lung biopsy is an interventional procedure performed to diagnose lung pathology by obtaining a small piece of lung which is examined under a microscope. Beyond microscopic examination for cellular morphology and architecture, special stains and ...

usually reveals non-necrotizing

granulomatous A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectiou ...

inflammation. It also shows "foamy" macrophages and crystals of oxalic acid. Hyperplasia tends to occur in type 1 pneumocytes and not in type 2 pneumocytes.

Treatment

Removing avian proteins

The only recommended long-term treatment is avoidance of the avian proteins that trigger BFL. This can stop the underlying inflammatory response, although symptoms may continue depending on existing damage. It is advisable to remove all

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and

and

pillow A pillow is a support of the body at rest for comfort, therapy, or decoration. Pillows are used in different variations by many species, including humans. Some types of pillows include throw pillows, body pillows, decorative pillows, and man ...

s containing feathers, from the patient's home, as well as any down-filled outerwear and

sleeping bag A sleeping bag is an insulated covering for a person, essentially a lightweight quilt that can be closed with a zipper or similar means to form a tube, which functions as lightweight, portable bedding in situations where a person is sleeping ...

s. It is also advisable to wash all soft furnishings, walls, ceilings and furniture, and to avoid future exposure to birds, bird droppings, or any items containing feathers, such as pillows in many hotels. In extreme cases, patients may be advised to evacuate their homes permanently and to dispose of all possessions that have been exposed to avian proteins if they cannot be cleaned thoroughly inside and out. (This includes books, beds, and upholstered furniture.) The patient should not attempt to clean any contaminated items. Anyone who comes in contact with items that have been near birds should change clothes and wash their hair before coming in contact with the patient.

Steroids

Corticosteroids, such as

, often suppresses symptoms temporarily, especially in the early stages of the disease. However, corticosteroids tend not to have a long-term effect if avian protein is not also removed from the environment. Dosage is chosen specific to each patient. By reducing

, corticosteroids might also delay

fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...

in the lungs.

Prognosis

Unless fibrosis has progressed beyond recovery, symptoms should improve, sometimes dramatically, in the absence of such allergens. Depending on the extent of fibrosis at the time of their diagnosis and how well they follow recommended treatment protocols (especially avoidance of allergens), many BFL patients make a full recovery. However, symptoms may recur quickly upon re-exposure to birds or related allergens.

Epidemiology

The frequency of BFL is hard to determine. It may be between 0.5% and 7.5% of bird-owners in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

References

External links

{{Medical resources , DiseasesDB = 29639 , ICD10 = {{ICD10, J, 67, 2, j, 60 , ICD9 = {{ICD9, 495.2 , ICDO = , OMIM = , MedlinePlus = , eMedicineSubj = , eMedicineTopic = , MeshID = D001716 , SNOMED CT = 69339004 Hypersensitivity pneumonitis