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Hypersensitivity Pneumonitis (HP)

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Presentation on theme: "Hypersensitivity Pneumonitis (HP)"— Presentation transcript:

1 Hypersensitivity Pneumonitis (HP)
By : ziba Loukzadeh, M.D Occupational Medicine department Yazd University of Medical Sciences

2 Definition Immune (hypersensitive) response
Extrinsic allergic alveolitis: granulomatous, interstitial, bronchiolar and alveolar-filling lung diseases caused by repeated exposure and subsequent sensitization to a variety of organic and chemical antigens

3 Etiology Microbial agents Animal proteins
Low molecular weight chemicals

4 Microbial agents Bacteria Fungi Ameba -Bagassosis
-Farmer’s lung -Bagassosis -Mushroom worker’s lung Fungi -Wood pulp worker’s lung -Cheese washer lung Ameba -Humidifier lung

5 Bacteria cause occupation Agent source Major antigen Farmer's lung
Agriculture worker Moldy hay thermoactinomycet Mushroom worker's Mushroom worker Compost Bagassosis Bagass worker Moldy sugarcane

6 Animal proteins Avian proteins : Bird breeder’s lung
Urine ,Serum ,Pelts : Animal handler’s lung Wheat weevil : Wheat weevil lung

7 Chemicals Isocyanate HP TDI , MDI , HDI TMA HP Trimellitic anhydride

8 Pathogenesis Immunology
Repeated inhalation of antigens sensitization immunology response(type III,IV) influx of neutrophiles shift T lymphocytes (~70%)(predominantly of CD8) Antibodies in HP are IgG class Response delay by 3-8 hours

9 Pathogenesis (cont’) Host factors -Polymorphism in TNF-α gene
-Non smokers > smokers -Polymorphism in TNF-α gene -No association with HLA

10 Pathogenesis (cont’) Exposure factors: -Ag concentration
-Duration of exp. -Frequency & intermittency of exp. -Particle size -Use of respiratory protection Farmer's lung disease: winter Bird breeder's lung: summer Indirect exposure

11 Clinical features Acute HP : fever ,chill ,myalgia ,cough & dyspnea + basilar rales in Ph/E (4-12 h after heavy exp. ) Recurrent febrile episodes (most frequent presentation) Subacute & chronic HP : insidious onset of respiratory symptoms ,malaise , fatigue , weight loss + basilar rales ,wheezing cyanosis ,right sided HF in Ph/E

12 DDx Inhalation fevers others granulomatous disorder(Sarcoidosis)
immunologic disease (Asthma) infection fibrotic lung disease (IPF)

13 Comparison HP& Inhalation fever
Feature HP Inhalation fever Example Farmer`s lung disease Metal fume fever Etiology Thermoactinomyces Zinc fume fever pathophysiology Hypersensitive reaction Cytokine- mediated (??) Exposure dose Low dose High dose Sensitization required Yes No

14 Comparison HP& Inhalation fever (cont´)
Feature HP Inhalation fever Fever Yes Flu-like syndrome Cough Expected Not necessary Dyspnea Not typically Chest exam Rales normal

15 Comparison HP& Inhalation fever (cont´)
Feature HP Inhalation fever CXR Alveolar infiltration No PFT Decreased DLCO&volums Minimal change BAL Lymocytosis Inincreased Neutrophiles Chronic sequle ~yes None Natural Hx Reccurent or progressive Complete recovery within 3 day

16 Lab. studies Precipitin Ab:
Helpful but not specific, not sensitive, not hallmark Leukocytosis ,mild elevation of ESR ,CRP , IgG , IgA ,IgM ,ACE ,ANA

17 PFT Normal (early dis.) Restrictive Obstructive Mixed
decreased DLCO (most sensitive physiologic test in early HP )

18 CXR Acute : diffuse ground glass ,fine nodular or reticulonodular pattern (lower lung ) Subacute : reticulonodular pattern Chronic : fibrosis ,reticular opacity, honey combing mediastinal lymphadenopathy (up to 50%)

19 HRCT Ground glass Centrilobular nodules Airspace consolidation
Mosaic patten Fibrosis Emphysema


21 Normal CXR







28 Histopathology Classic triad : cellular bronchiolitis
lymphoplasmocytic interstitial infiltration non-necrotizing granuloma

29 diagnosis Temporal relationship between symptoms and certain activities is often the first clue to the diagnosis of HP

30 diagnosis environmental history: pets and other domestic animals
hobbies such as gardening and lawn care recreational activities, for example, use of hot tubs and indoor swimming pools use of humidifiers, cool mist vaporizers, and humidified air conditioners moisture indicators such as leaking, flooding, or previous water damage to carpets and furnishings

31 Diagnostic criteria Required appropriate exposure Supportive
dyspnea on exertion inspiratory crackles lymphocytic alveolitis Supportive recurrent febrile episodes infiltrative on CXR decreased DLCO precipitating antibodies granulomatous on lung biopsy improvement with contact avoidance

32 Treatment Best treatment : Removal from exp.
Preferred approach : Elimination of Ag. Oral corticosteroid : in severe or progressive disease O2 ,inhaled steroid & B-agonist in airflow limitation


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