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Farmer's Lung

Farmer's Lung Disease

Farmer's lung, one of the most common forms of hypersensitivity pneumonitis, develops due to inhalation of thermophilic microorganisms (present in hay or grain dust) that produce a proinflammatory reaction. Depending on the severity of exposure, patients can suffer from acute, subacute, or chronic respiratory (dyspnea, cough) and constitutional symptoms, as well as fever. Recognition rests on identifying the patient's profession and associated risk factors, whereas imaging and immunology studies are necessary to confirm the diagnosis.


Presentation

Farmer's lung, as a separate clinical entity, is one of the subtypes of hypersensitivity pneumonitis (HP), an autoimmune-mediated disorder of the lung parenchyma [1] [2]. The pathogenesis starts with inhalation of dust from hay or grain containing thermophilic microorganisms (temperatures between 40-60 degrees celsius are optimal for their growth), most commonly occurring under two circumstances - in late winter months when farmers handle very large quantities of hay for feeding purposes; and in very damp and humid conditions (from heavy rain), which are favorable for thermophilic microbial growth [1] [3]. Thermoactinomyces species (T. sacchari, T. vulgaris, T. viridis) and Saccharopolyspora rectivirgula are notable bacterial pathogens, whereas several fungal species (Aspergillus and Penicillium) have been linked to farmer's lung as well [1] [4]. When these microorganisms are inhaled, a hypersensitivity reaction leads to the formation of antigen-antibody immune complexes and the appearance of symptoms [1]. On the basis of several factors (severity of exposure, duration, etc.), three distinct clinical courses have been described [1] [2] [5]:

  • Acute - After severe exposure to very large quantities of microorganisms, respiratory symptoms in the form of rapidly progressing dyspnea with a cough appear within several hours and are sometimes accompanied by fever and malaise [1] [5]. Resolution of symptoms is seen after a period of several days [6]. Recurrences of the acute form of farmer's lung have been described in patients with preexisting chronic obstructive pulmonary disease (COPD) [6].
  • Subacute - A somewhat less severe clinical course is encountered in the subacute form of farmer's lung, characterized by general malaise, asthenia, anorexia, dyspnea and cough [1] [5].
  • Chronic - Prolonged exposure to lower concentrations results in chronic and insidious symptoms. Chronic farmer's lung, which may last for weeks or months, manifests as a slowly progressive dyspnea on exertion, a dry cough, together with weight loss, fatigue, and digital clubbing [1] [5].
Exposure to Moldy Hay
  • Asymptomatic farmers (n 12) and normal volunteers with no prior exposure to moldy hay (n 15) were used as control subjects.[ncbi.nlm.nih.gov]
  • To diagnose Farmer's Lung, the treating physician will first take a detailed history, especially the occupational history to look for exposure to moldy hay.[epainassist.com]
  • Usually, people with Farmer's Lung do not associate their health problem with exposure to moldy hay. Instead, they go to their doctors complaining of breathing problems.[ccohs.ca]
Pulmonary Disorder
  • Definition of farmer's lung : an acute pulmonary disorder characterized by sudden onset, fever, cough, expectoration, and breathlessness that results from the inhalation of spores in dust from moldy hay or straw First Known Use of farmer's lung 1945,[merriam-webster.com]
  • Farmer’s lung , also called thresher’s lung or harvester’s lung , a pulmonary disorder that results from the development of hypersensitivity to inhaled dust from moldy hay or other fodder.[britannica.com]
  • Farmer’s lung, also called thresher’s lung or harvester’s lung, a pulmonary disorder that results from the development of hypersensitivity to inhaled dust from moldy hay or other fodder.[britannica.com]
  • Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, represents a group of pulmonary disorders mediated by an inflammatory reaction to inhalation of an allergen.[radiopaedia.org]
Rales
  • The clinical features were fatigability, weight loss, recurrent fever, dry cough, pulmonary rales, and clubbing. Serologic studies for precipitins to Micropolyspora faeni were positive.[ncbi.nlm.nih.gov]
Severe Clinical Course
  • Subacute - A somewhat less severe clinical course is encountered in the subacute form of farmer's lung, characterized by general malaise, asthenia, anorexia, dyspnea and cough.[symptoma.com]

Workup

The diagnosis of farmer's lung can be made only if adequate clinical suspicion is raised, which should be based on information obtained from a detailed patient history and thorough physical examination. During history taking, the physician must gather data about the patient's occupancy, in order to assess potential exposure to thermophilic pathogens [1]. The physical examination may further aid in making a presumptive diagnosis by detecting dry crackles when auscultating the lungs [1]. After a careful assessment of signs and symptoms, imaging studies should be ordered. Plain radiography is usually the first radiograph employed, showing diffuse infiltrates in a ground glass pattern and patchy opacities, but high-resolution computed tomography (HRCT) is the gold standard for evaluation of the lung parenchyma in patients suffering from hypersensitivity pneumonitis [1] [5]. In addition to imaging studies, laboratory testing for precipitating immunoglobulin (Ig) G antibodies, skin prick testing, bronchial challenge testing using appropriate antigens, and spirometry are constitutive features of the workup [1] [3] [5]. Some authors advocate that a transbronchial biopsy (TBB) with subsequent histopathological examination should be obtained in order to solidify the diagnosis [1].

Pulmonary Infiltrate
  • FARMER'S lung resembles Loeffler's syndrome, for, at times, it manifests the triad of pulmonary infiltrations, eosinophilia and a benign clinical course.[nejm.org]
Micropolyspora Faeni
  • Massive amounts of mould spores were cultured from the residential areas, and, in addition, the male patient had an elevated titer to Micropolyspora faeni and the female patient, elevated titers to Thermoactinomyces vulgaris, Micropolyspora faeni, Aspergillus[ncbi.nlm.nih.gov]
  • Serologic studies for precipitins to Micropolyspora faeni were positive. The chest roentgenogram showed a ground-glass appearance with air bronchogram.[ncbi.nlm.nih.gov]
  • Abstract An antigen fraction from Faenia rectivirgula (Micropolyspora faeni) having diagnostic significance for farmer's lung disease was isolated by Sephadex G-200 and G-100 fractionations.[ncbi.nlm.nih.gov]
  • The patient had precipitating antibodies against several species of hay molds, especially Micropolyspora faeni, and immune complex deposition in the lung.[ncbi.nlm.nih.gov]
  • faeni, and compared with contemporary lung function parameters.[ncbi.nlm.nih.gov]
Thermoactinomyces Vulgaris
  • vulgaris, in addition to spirometry, pulmonary diffusing capacity (DL(CO)), and the evaluation of chronic bronchitis.[ncbi.nlm.nih.gov]
  • Abstract Sequential serum samples of 13 patients with acute farmer's lung (FL) taken during a follow-up of 18-36 months, were tested for antibodies of immunoglobulin G (IgG), IgA, IgM and IgE classes against Thermoactinomyces vulgaris and Micropolyspora[ncbi.nlm.nih.gov]
  • The main pathogen was Thermoactinomyces vulgaris. The factors which influenced farmer's lung were the moldy state of the hay and the dust concentration.[ncbi.nlm.nih.gov]
  • Precipitating antibodies against Thermoactinomyces vulgaris and T. thalpophilus were observed only in 1.5% and 0.5% of the subjects, respectively. Two subjects concomitantly demonstrated F. rectivirgula and T. vulgaris-specific serum precipitins.[ncbi.nlm.nih.gov]
  • Massive amounts of mould spores were cultured from the residential areas, and, in addition, the male patient had an elevated titer to Micropolyspora faeni and the female patient, elevated titers to Thermoactinomyces vulgaris, Micropolyspora faeni, Aspergillus[ncbi.nlm.nih.gov]

Treatment

  • Twenty patients were given prednisolone treatment for 8 wk. Sixteen patients received an 8-wk placebo treatment. One patient was withdrawn from the analysis when she terminated corticosteroid treatment because of side effects.[ncbi.nlm.nih.gov]
  • In eight subjects tested after one month of treatment the level of SP-A was unchanged although all were clinically improved.[ncbi.nlm.nih.gov]
  • Corticosteroid treatment had no effect on long term prognosis. There was no difference in the recovery of lung function between those who returned to work compared with those who did not.[ncbi.nlm.nih.gov]
  • The main treatment is avoidance of the antigen, so it is essential to educate patients on preventive measures. To date, no controlled studies have assessed the role of immunosuppressive therapy in this disease.[ncbi.nlm.nih.gov]
  • What Are The Treatments For Farmer's Lung? The gold standard for treatment for Farmer' Lung is to stay away from moldy hay.[epainassist.com]

Prognosis

  • We compared the clinical findings and the prognosis between 12 smokers (SM-FLD) and 31 non-smokers with FLD (NS-FLD).[ncbi.nlm.nih.gov]
  • Corticosteroid treatment had no effect on long term prognosis. There was no difference in the recovery of lung function between those who returned to work compared with those who did not.[ncbi.nlm.nih.gov]
  • The aim of this study was to describe clinical characteristics, evolution and factors that influence the prognosis of patients with FLD.[ncbi.nlm.nih.gov]
  • […] dust from feathers and faeces mushroom worker's lung is an allergic response to thermophilic actinomycetes spores in mould maltworker's lung - Aspergillus clavatus spores Links: pathology aetiology clinical features investigations diagnosis management prognosis[gpnotebook.co.uk]
  • Also Read: Byssinosis or Brown Lung Disease or Monday Fever: Causes, Signs, Symptoms, Diagnosis, Treatment, Prognosis Pneumoconiosis or Black Lung Disease: Symptoms, Diagnosis, Treatment, Prevention, Who is at Risk Bird Fancier's Lung: Causes, Symptoms[epainassist.com]

Etiology

  • Abstract To confirm the main etiological antigen of farmer's lung in Dafeng County, Jiangsu Province, People's Republic of China, precipitins in serum from 30 patients with farmer's lung were tested with several strains of antigens.[ncbi.nlm.nih.gov]
  • In the absence of the primary recognized FLD agent, Saccharopolyspora rectivirgula, its etiology remains unknown. A prospective case-control study was performed to find the etiology of FLD in this area.[ncbi.nlm.nih.gov]
  • This study adds to the growing body of evidence that L. corymbifera should be recognized as an etiologic agent of FLD along with S. rectivirgula.[ncbi.nlm.nih.gov]
  • This study allowed clarification of the factors that influence the microbial concentration of hay with etiological agents of FLD.[ncbi.nlm.nih.gov]
  • Some etiologic agents in Hypersensitivity Pneumonitis Major antigen or microbe Source of exposureDisease MicropolysporafaeniMoldy hayFarmer's lung Micropolysporafaeni, Thermoactinomyces vulgaris Moldy grainGrain handler's lung ThermoactinomycessacchariMoldy[slideshare.net]

Epidemiology

  • The epidemiological features of farmer's lung are analyzed and discussed and certain preventive measures are suggested.[ncbi.nlm.nih.gov]
  • A comprehensive epidemiological survey is indicated to determine the prevalence of FL in different geo-climatic regions of the country.[ncbi.nlm.nih.gov]
  • Abstract We performed a nationwide epidemiologic study of hypersensitivity pneumonitis (HP) in Japan by questionnaire and found that 835 cases of HP were recognized during the 1980s; 74.4% were summer-type HP, 8.1% farmer's lung, 4.3% ventilation pneumonitis[ncbi.nlm.nih.gov]
  • Abstract A prospective study was undertaken by the Departments of Respiratory Medicine and Medical Microbiology at the Cork University Hospital, a. to investigate the epidemiology of Farmer's Lung (F.L.) in the Republic of Ireland (pop. 3.5 million),[ncbi.nlm.nih.gov]
  • Abstract The objectives of this epidemiological study were to evaluate the prevalence of farmer's lung disease (FLD) and to explore the potential risk factors for FLD among Chinese greenhouse farmers.[ncbi.nlm.nih.gov]
Sex distribution
Age distribution

Pathophysiology

  • This is in accordance with both the pathophysiological behaviour of the inhaled particulate antigen and the subsequent distribution of pulmonary changes in chronic farmer's lung.[ncbi.nlm.nih.gov]
  • The aim of this study was to gain new insights into the pathophysiology of acute farmer's lung using cardiopulmonary exercise testing.[ncbi.nlm.nih.gov]
  • •Introduction •Definition •Aetiology •Pathophysiology •Clinical picture •Smoking •Investigations •Diagnostic criteria •Differential diagnosis •Treatment •Prognosis 3. Introduction 4.[slideshare.net]
  • Pathophysiology Extrinsic allergic alveolitis is caused by inhalation of antigens that cause a hypersensitivity reaction in the respiratory system.[news-medical.net]

Prevention

  • Our purpose was to determine whether and to what extent the use of such masks reduced or prevented symptoms in affected patients.[ncbi.nlm.nih.gov]
  • Clearly, the risks of ignoring these preventive measures are not worth taking.[nasdonline.org]
  • The main treatment is avoidance of the antigen, so it is essential to educate patients on preventive measures. To date, no controlled studies have assessed the role of immunosuppressive therapy in this disease.[ncbi.nlm.nih.gov]
  • In this study, we evaluated the practicality of dust masks and their effectiveness in prevention of FLD.[ncbi.nlm.nih.gov]
  • The epidemiological features of farmer's lung are analyzed and discussed and certain preventive measures are suggested.[ncbi.nlm.nih.gov]

References

Article

  1. Cano-Jiménez E, Acuña A, Botana MI, et al. Farmer's Lung Disease. A Review. Arch Bronconeumol. 2016;52(6):321-328.
  2. Selman M, Pardo A, King TE. Hypersensitivity pneumonitis: insights in diagnosis and pathobiology. Am J Respir Crit Care Med. 2012;15:314–324.
  3. Bourke SJ, Dalphin JC, Boyd G, McSharry C, Baldwin CI, Calvert JE. Hypersensitivity pneumonitis: current concepts. Eur Respir J Suppl. 2001;32:81s–92s
  4. Spagnolo P, Rossi G, Cavazza A, et al. Hypersensitivity Pneumonitis: A Comprehensive Review. J Investig Allergol Clin Immunol. 2015;25(4):237-250.
  5. Lacasse Y, Cormier Y. Hypersensitivity pneumonitis. Orphanet J Rare Dis. 2006;1:25.
  6. Malinen AP, Erkinjuntti-Pekkanen RA, Partanen PLK, Rytkönen HT, Vanninen RL. Long-term sequelae of farmer’s lung disease in HRCT: a 14-year followup study of 88 patients and 83 matched control farmers. Eur Radiol. 2003;13: 2212–21.

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Last updated: 2019-07-11 22:20