It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax. The following descriptions are intended to provide a summary of HRCT findings that are 1) highly suggestive of HP, which we categorize as “typical HP”; 2) less frequently reported but compatible with HP, which we refer to as “compatible with HP”; or 3) “indeterminate for HP” when the HRCT findings are neither suggestive nor compatible with features of HP. (B) Another photomicrograph illustrating giant cells in a patient with HP. The following are common signs and symptoms of acute, subacute, and chronic hypersensitivity pneumonitis. Analysis of lung changes at expiration may increase diagnostic confidence in nonfibrotic HP and is necessary for better characterization of heterogeneous lung attenuation in both forms of the disease. For patients with clinical and radiographic manifestations suggestive of fibrotic HP (i.e., patients with radiological and/or histopathological evidence of fibrosis), the guideline committee: ii. Regardless of which CPG is followed, the initial steps are similar, and ongoing diagnostic evaluation may be redirected on the basis of the MDD. Inclusion of TBBx in the multimodality diagnostic approach of patients with ILD increased the likelihood of arriving at a diagnosis compared with an approach without TBBx (RR, 1.67; 95% CI, 1.21–2.30). Occasionally, lung transplants are used to treat severe chronic disease in some patients. Magnification, 63×. Table 4. Purely emphysematous forms of HP can be seen independently of smoking history (Figure E7) (85, 116, 131, 132), and fibrotic HP may also be diagnosed at the time of an acute exacerbation (Figure E8) (133). Contaminated raw materials in food-processing industry, Contaminated domestic ventilation and cooling systems, Contaminated misting fountains and humidifiers, Baker’s yeast, brewer’s yeast, wine yeasts, Endotoxin from pool-water sprays and fountains, Contaminated humidifiers and air-conditioning systems, Parakeets, canaries, budgerigars, pigeons, parrots, chicken, turkeys, geese, ducks, wild birds, pheasants, Bird fancier’s disease, bird breeder’s disease, pigeon breeder’s lung, chicken breeder’s lung, Shell protein (oyster, sea snail, mussels), Shellfish alveolitis, oyster-shell HP, mollusk-shell HP, Rat and desert mouse (gerbil) urine, serum, pelts, Cosmetics, unsaturated fatty acids, phytosterol, Wood (cabreuva, cedar, mahogany, pine, ramin, umbrella pine), Acid anhydrides (pyromellitic and trimellitic anhydrides), Polyurethane foams, spray paints, elastomers, glues, adhesives, mattresses, car parts, shoes, imitation leather, rubber products, chipboards, elastic synthetic fibers, electrical insulations, Degreasing agents, cleaning agents, extraction agents, Coolant fluid in laser hair-removal devices, Isocyanates (toluene diisocyanate, methylene diphenyl diisocyanate, hexamethylene diisocyanate, MIC, NDI, polyisocyanate), Tetrachlorophthalic and hexahydrophthalic acid, Organometallic compound for semiconductors used in industry. There are many similarities in the initial presentation of patients with fibrotic ILD. Lymphoid aggregates, especially those with secondary germinal centers, are either absent or very focal and relatively inconspicuous. Common symptoms and signs of both nonfibrotic and fibrotic HP include dyspnea, cough, and midinspiratory squeaks (or chirping rales or squawks) (32). §§Definition and Diagnostic Criteria sections leader. In support of our mission, we are committed to advancing research on interstitial lung diseases including hypersensitivity pneumonitis. served on an advisory committee, served as a speaker, and received research support from Boehringer Ingelheim; and served as a consultant for Boehringer Ingelheim and Orinove. served on an advisory committee for Boehringer Ingelheim and Roche; served as a consultant for Galapagos, OSIC, and Sanofi; served as a speaker for Bracco; and received research support from Boehringer Ingelheim. These substances include certain: Learn more about common environmental sources of substances that may cause your condition. Adequate specimens were obtained in 87% (95% CI, 79–96%) of sampling procedures. The approach should be reevaluated as new evidence accumulates. suggests transbronchial forceps lung biopsy (suggestion, very low confidence in the estimated effects). Different choices will be appropriate for different patients, and you must help each patient arrive at a management decision consistent with her or his values and preferences. The latter features are usually observed in less fibrotic lung tissue. 2. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. The optimal chest HRCT scan for characterizing HP should be a noncontrast examination, except in the context of acute respiratory decline, in which case CT angiography may be justified to detect acute pulmonary embolisms. Conversely, patients with fibrotic HP are less likely to have an identified exposure and more frequently have an insidious and chronic onset of isolated pulmonary symptoms, fibrotic changes with or without more specific features of HP on chest imaging, and a nonspecific differential cell profile on BAL analysis (4, 105–107). Prevalence of HP is highest among older individuals (i.e., 65 yr and older, with the average patient receiving a diagnosis in their fifth or sixth decade) (34). The studies that enrolled patients with known HP did not report adverse outcomes. Another study enrolled 46 patients with IPF and used a nine-item questionnaire, serum IgG testing against HP-associated antigens, and bronchial-challenge testing to identify potential inciting agents of HP. • Combination of areas of low and high attenuation that can correspond to two main situations: a. Symptoms may include shortness of breath, tiredness, coughing that lasts weeks or months and weight loss that gets progressively worse. This pattern emphasizes the diagnostic value of lobules with decreased attenuation and vascularity on inspiratory HRCT images, especially when concomitant with air trapping at expiration, both suggesting the presence of severe bronchiolar obstruction. Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is one of the most common interstitial lung diseases (ILDs) 1, 2. Table 3. Respiratory infection and delayed wound healing were complications in 3% (95% CI, 2–3%) and 3% (95% CI, 1–5%), respectively. (E) High-magnification photomicrograph showing a well-formed nonnecrotizing granuloma in a surgical lung biopsy specimen from a patient with sarcoidosis. The inflammatory infiltrate is typically polymorphic in that it includes smaller numbers of plasma cells and occasionally eosinophils in some patients. The proportion of HP among all ILD cases varies tremendously, ranging from 2% to 47% in studies and registries (35, 59–67). Less frequently, there may be constitutional symptoms such as weight loss, flu-like symptoms (chills, low-grade fever, and malaise), chest tightness, and wheezing, as well as physical examination findings of rales and cyanosis (1). Finally, for distinguishing nonfibrotic HP from sarcoidosis, BAL fluid lymphocyte thresholds of 20%, 30%, and 40% yielded sensitivities of 95%, 88%, and 76%, respectively, and specificities of 26%, 43%, and 61% respectively, with an area under the curve of 0.71 (95% CI, 0.67–0.74). 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