Case of the Week: Hypersensitivity pneumonitis

 

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Diagnosis: Hypersensitivity pneumonitis AKA extrinsic allergic alveolitis.

File: 2A          
Organ system: 2.0 Thoracic
Organ: A. Lungs

Information:
Etiology and incidence: 1) Specific antigens for immune complex disease (Type III an Type IV reactions); 2) Inflammation of the alveoli caused by hypersensitivity to inhaled organic dusts. Patients exposed to the dust by their occupation or hobbies.

Bird fancier’s lung

Avian proteins Feathers and bird droppings

Bagassosis

Thermophilic actinomycetes (contamination with Thermoactinomyces sacchari / vulgaris and Micropolyspora faeni) Moldy bagasse (pressed sugarcane)  from moldy sugar cane in sugar mill

Berylliosis

Beryllium Electronics industry

Cheese-washer’s lung

Penicillum casei or P.roqueforti Cheese casings

Compost lung

Aspergillus Compost

Crack lung

Crack cocaine Heavy crack smoking

Farmer’s lung

The molds Thermophilic actinomycetes Saccharopolyspora rectivirgula, and Micropolyspora faeni Moldy hay

Farmer’s lung

from moldy hay (Thermoactinomyces vulgaris or Micropolyspora faeni)

Hot tub lung

Mycobacterium avium complex Mist from hot tubs.

Isocyanate HP

TDI, HDI, and MDI Paints, resins, and polyurethane foams.

Japanese summer house HP

Trichosporon cutaneum Damp wood and mats

Malt worker’s lung

Aspergillus clavatus Moldy barley

Malt worker’s lung

malt dust (Aspergillus clarvatus)

Maple bark disease

Cryptostroma corticale Moldy maple bark

Maple bark disease

from moldy maple bark in saw mill (Cryptostroma corticale)

Metalworking fluids HP

Nontuberculous Mycobacteria. Mist from metalworking fluids.

Miller’s lung

Sitophilus granarius (wheat weevil) Dust-contaminated grain

Mollusc shell HP

Aquatic animal proteins Mollusc shell dust.

Mushroom worker’s lung

Thermophilic actinomycetes or Micropolyspora faen Mushroom compost

Pandora’s pneumonitis

from forced‑air equipment = with heating / humidifying / air conditioning systems (thermophilic actinomycetes)

Peat moss worker’s lung

Caused by Monocillium sp. and Penicillium citreonigrum Peat moss

Penguin Humidifier lung

The bacteria, T. candidus, Bacillus subtilis, B. cereus, and Klebsiella oxytoca; Thermophilic actinomycetes the fungi, Aureobasidium pullulans; and the amoebae Naegleria gruberi, Acanthamoeba polyhaga, and Acanthamoeba castellani. Mist generated by a machine from standing water

Sequolosis

from redwood dust (Graphium species)

Suberosis

Penicillum frequentans Moldy cork dust

Suberosis

from moldy cork dust (Penicillium frequentans)

TMA HP

Trimellitic anhydride Plastics, resins, and paints.

Wine-grower’s lung

Botrytis cinerea mold Moldy grapes

Diagnosis: 1) Clinical: a) Acute; Symptoms may develop 4–6 hours following heavy exposure to the provoking antigen. Fever, chills, malaise, cough, chest tightness, dyspnea, and headache. Symptoms resolve within 12 hours to several days upon cessation of exposure; b) Subacute; Patients gradually develop a productive cough, dyspnea, fatigue, anorexia, weight loss, and pleurisy. Symptoms are similar to the acute form of the disease, but less severe and last longer; c) Chronic; Patients often lack history of acute episodes. Insidious onset of cough, progressive dyspnea, fatigue, and weight loss associated with partial to complete but gradual reversibility. Avoiding any further exposure is recommended. Clubbing observed in 50% of patients. Tachypnea, respiratory distress, and inspiratory crackles over lower lung fields often are present. Many patients have hypoxemia at rest, and all patients desaturate with exercise. 2) Radiology: a) General: i) Chest radiographs are often normal in patientswith mild symptoms and can remain normal; ii)CXRs: when abnormal usuallyshow bilateral areas of increased opacity that may be eitherheterogeneous or homogeneous, simulating pulmonary edema . Typically seen in midto lower lung zones with sparing of costophrenic angles.Less common findings include focal areas of homogeneousopacity mimicking and small poorlydefined nodules; iii) HRCT:  Half of patients with normal chest radiographshave characteristic findings of centrilobular ground-glass andnodular opacities on CT; b) Acute: i) CXRs: nodular interstitial pattern (at times with ground-glass density in the lower and middle lung zones) may be observed. Findings are normal in approximately 10% of patients”; ii) HRCT: ground-glass opacities or diffusely increased radiodensities are present. Pulmonary function tests show reduced diffusion capacity of lungs for carbon monoxide (DLCO). Many patients have hypoxemia at rest, and all patients desaturate with exercise; c) Subacute; i) Considerable overlap in the radiographic findings ofacute and subacute hypersensitivity pneumonitis. In transition from acute to subacute disease, poorlydefined air-space opacities may be replaced by well-definedreticular or nodular opacities. The nodulesmay be so well defined that they mimic the findings of miliarytuberculosis or pulmonary metastases; ii) CXRs: As with acute disease, chest radiographs may be normal in patients with subacute disease. Micronodular or reticular opacities are most prominent in mid-to-lower lung zones. Findings may be present in patients who have experienced repeated acute attacks. HRCT: ground-glass andnodular opacities in a centrilobular distribution. Irregular linear opacitiesare less common. Air trapping on expiratory thin-sectionimages is a helpful ancillary finding, reflecting associatedbronchiolitis .Diagnosis of subacute HP is based on the presence of ground-glass opacities, poorly defined centrilobular nodules, and mosaic attenuation on inspiratory images and of air trapping on expiratory CT images; d) Chronic: CXRs: progressive fibrotic changes with loss of lung volume particularly affect the upper lobes. Nodular or ground-glass opacities are not present. HRCT: emphysema are found on significant chest films and CT scans. Chronic interstitial inflammation and alveolar destruction (honeycombing) associated with dense fibrosis. Chronic HP is characterized on high-resolution CT by the presence of reticulation due to fibrosis superimposed on findings of subacute HP. The characteristic mid to upperlobe distribution and the finding of small nodules on CT imageshelp distinguish chronic hypersensitivity pneumonitis fromidiopathic pulmonary fibrosis. Occasionally, however, mid tolower lung zone fibrosis without nodularity is seen; such casesare radiologically indistinguishable from idiopathic pulmonaryfibrosis.

Prognosis: The most important treatment is to remove the patient from the source.  Steroids are used for the inflammation. The long-term prognosis is usually good, but some patients develop severe respiratory insufficiency, and a few die of the disease.

References:
Chronic Hypersensitivity Pneumonitis: CT Features—Comparison with Pathologic Evidence of Fibrosis and Survival Radiology August 2007 244:591-598; doi:10.1148/radiol.2442060640
Hakan Sahin, Kevin K. Brown, Douglas Curran-Everett, Valerie Hale, Carlyne D. Cool, Jason S. Vourlekis, and David A. Lynch
Abstract 
Full Text 
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Chronic Hypersensitivity Pneumonitis: Differentiation from Idiopathic Pulmonary Fibrosis and Nonspecific Interstitial Pneumonia by Using Thin-Section CT Radiology January 2008 246:288-297; doi:10.1148/radiol.2453061881
C. Isabela S. Silva, Nestor L. Müller, David A. Lynch, Douglas Curran-Everett, Kevin K. Brown, Kyung Soo Lee, Man Pyo Chung, and Andrew Churg
Abstract 
Full Text 
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Continuing Medical Education: Hypersensitivity Pneumonitis: A Historical, Clinical, and Radiologic Review Radiographics November 2009 29:1921-1938; doi:10.1148/rg.297095707
Jan V. Hirschmann, Sudhakar N. J. Pipavath, and J. David Godwin
Abstract 
Full Text 
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Imaging of Occupational Lung Disease Radiographics November 2001 21:1371-1391
Kun-Il Kim, Chang Won Kim, Min Ki Lee, Kyung Soo Lee, Choong-Ki Park, Seok Jin Choi, and Jong Gi Kim
Abstract 
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Biopsy-proved Idiopathic Pulmonary Fibrosis: Spectrum of Nondiagnostic Thin-Section CT Diagnoses Radiology March 2010 254:957-964; doi:10.1148/radiol.0990898

Nicola Sverzellati, Athol U. Wells, Sara Tomassetti, Sujal R. Desai, Susan J. Copley, Zelena A. Aziz, Maurizio Zompatori, Marco Chilosi, Andrew G. Nicholson, Venerino Poletti, and David M. Hansell
Abstract 
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Eosinophilic Lung Diseases: Diagnostic Accuracy of Thin-Section CT in 111 Patients Radiology September 2000 216:773-780

Takeshi Johkoh, Nestor L. Müller, Masanori Akira, Kazuya Ichikado, Moritaka Suga, Masayuki Ando, Takeshi Yoshinaga, Teisou Kiyama, Naoki Mihara, Osamu Honda, Noriyuki Tomiyama, and Hironobu Nakamura
Abstract 
Full Text 
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Hypersensitivity Pneumonitis: Spectrum of High-Resolution CT and Pathologic Findings
C. Isabela S. Silva, Andrew Churg and Nestor L. Müller.
http://www.ajronline.org/content/188/2/334.abstract 

Table 13-5 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (2007). Robbins Basic Pathology. Philadelphia: Saunders. ISBN 1-4160-2973-7.  8th edition.

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