Hyprsensitivity pneumonitis (HP) also known asExtrinsic allergic alveolitis is a non Ig E mediated immune lung disease resultingfrom the sensitization and recurrent exposure to any of a wide variety oforganic dust 1.Incidence of HP is highly variable and related to exposurerisk. The antigens that cause HP can be classified as coming from microbial (fungalor bacterial), animal or chemical sources. Antigens associated with HP aresmaller than 3 µm , allowing them to be deposited in distal airways andalveolar spaces. Hypersensitiviy pnemonitis is known to contribute to 5 -15% of ILDburden 2 HP is histologically characterized by the triad ofnon necrotizing granuloma, chronic inflammatory change in smaller airways and diffuseinterstitial infiltrates of chronic inflammatory cells 3Bird Fancier,s lung disease(BFL) is a type of lungdisease caused by air borne exposure to avian antigens4,5.BFL is probablyone of the most common types of HP and is mainly described amoung pigeon andbudgerigar fanciers6.Classically, the clinicalpresentation has been divided into acute , sub acute and chronic formsdepending on the amount of inhaled antigen and repeated exposure.
7 Acute form presents after high levelof exposure and the symptoms develop within 4 to 8 hours in the form of highgrade fever with chills , muscle pains , fatigue and a non productive cough. Subacute form is due to relatively low levels of exposure and the symptoms aremore insidious. Chronic HP results from prolonged low level exposure to theantigens which lead to irreversible pulmonary damage without acute attacks 8. Acuteand sub acute form of disease may resolve by the avoidance of exposure .ChronicHP is a potentially severe disease which may be progressive , irreversible ,and result in debilitating fibrotic lung disease9It may lead to respiratory failure.Prompt diagnosis of HP is important, as the diseaseis reversible when diagnosed early in its course.
Diagnosisof HP remains heavily dependent on clinical judgment and there is no specific immunological,radiological or physiological diagnostic test for HP.Correct diagnosis is based upon exposure history,clinical assessment, radiographic and physiologic finding and if possible, theresult of removal of the patient from the suspected etiologic exposure. Othertests, such as bronchoalveolar lavage (BAL) and lung biopsy, are helpful in rulingout other potential diagnoses and in lending further support to the diagnosisof HP. Thecharacteristic BAL found in hypersensitivity pneumonitis (HP) is alymphocytosis, though we did not have facility to perform BAL full report onour patient.
HRCT is useful in diagnosing and separating theclinical forms of HP. HRCT may be normal in patients with symptomatic acute HP 10.When abnormal, the predominant findings are ground-glass opacities or poorlydefined small nodules 1112.Diffuse areas of dense air-space consolidationmay be associated with ground-glass opacities12. Because of the considerable overlap in clinicalcases of sub acute and chronic HP, the HRCT patterns are more variable.Ground-glass opacities or poorly defined small nodules are commonly found in subacute HP. In fact, HRCT of our patient does notreveal typical features of sub acute hypersensitivity pneumonitis which areground-glass opacities, airtrapping, and centrilobular ground-glass opacities.
DistinctiveHRCT findings in chronic HP are the combination of reticular, ground-glass, andcentrilobular nodular opacities associated with signs of “fibrosis” (i.e.,interlobular septal thickening, lobar volume loss, traction bronchiectasis, andhoneycombing) 11. Treatmentstrategies include environmental control and medical therapy. Antigen avoidanceand removal remains the single most important facet in the treatment of BFL andis crucial in its management 15.
Continued exposure leads to persistentsymptoms and progressive lung damage. Acute & sub acute form of disease mayresolve by the avoidance of exposure. Corticosteroids are indicatedfor the treatment of severe acute and sub-acute HP and for chronic HP that issevere or progressive. As our patient had small joint stiffness along withpositive Rheumatoid factor, Rheuma