Hyprsensitivity develop within 4 to 8 hours in

Hyprsensitivity pneumonitis (HP) also known as
Extrinsic allergic alveolitis is a non Ig E mediated immune lung disease resulting
from the sensitization and recurrent exposure to any of a wide variety of
organic dust 1.Incidence of HP is highly variable and related to exposure
risk. The antigens that cause HP can be classified as coming from microbial (fungal
or bacterial), animal or chemical sources. Antigens associated with HP are
smaller than 3 µm , allowing them to be deposited in distal airways and
alveolar spaces. Hypersensitiviy pnemonitis is known to contribute to 5 -15% of ILD
burden 2

 

HP is histologically characterized by the triad of
non necrotizing granuloma, chronic inflammatory change in smaller airways and diffuse
interstitial infiltrates of chronic inflammatory cells 3

Bird Fancier,s lung disease(BFL) is a type of lung
disease caused by air borne exposure to avian antigens4,5.BFL is probably
one of the most common types of HP and is mainly described amoung pigeon and
budgerigar fanciers6.

Classically, the clinical
presentation has been divided into acute , sub acute and chronic forms
depending on the amount of inhaled antigen and repeated exposure.7

 

Acute form presents after high level
of exposure and the symptoms develop within 4 to 8 hours in the form of high
grade fever with chills , muscle pains , fatigue and a non productive cough. Sub
acute form is due to relatively low levels of exposure and the symptoms are
more insidious. Chronic HP results from prolonged low level exposure to the
antigens which lead to irreversible pulmonary damage without acute attacks 8.

 

Acute
and sub acute form of disease may resolve by the avoidance of exposure .Chronic
HP 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 disease
is reversible when diagnosed early in its course.

Diagnosis
of 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, the
result of removal of the patient from the suspected etiologic exposure. Other
tests, such as bronchoalveolar lavage (BAL) and lung biopsy, are helpful in ruling
out other potential diagnoses and in lending further support to the diagnosis
of HP. The
characteristic BAL found in hypersensitivity pneumonitis (HP) is a
lymphocytosis, though we did not have facility to perform BAL full report on
our patient.  

HRCT is useful in diagnosing and separating the
clinical forms of HP. HRCT may be normal in patients with symptomatic acute HP 10.
When abnormal, the predominant findings are ground-glass opacities or poorly
defined small nodules 1112.Diffuse areas of dense air-space consolidation
may be associated with ground-glass opacities12.

Because of the considerable overlap in clinical
cases of sub acute and chronic HP, the HRCT patterns are more variable.
Ground-glass opacities or poorly defined small nodules are commonly found in sub
acute HP. In fact, HRCT of our patient does not
reveal typical features of sub acute hypersensitivity pneumonitis which are
ground-glass opacities, air
trapping, and centrilobular ground-glass opacities.

Distinctive
HRCT findings in chronic HP are the combination of reticular, ground-glass, and
centrilobular nodular opacities associated with signs of “fibrosis” (i.e.,
interlobular septal thickening, lobar volume loss, traction bronchiectasis, and
honeycombing) 11.

 Treatment
strategies include environmental control and medical therapy. Antigen avoidance
and removal remains the single most important facet in the treatment of BFL and
is crucial in its management 15. Continued exposure leads to persistent
symptoms and progressive lung damage. Acute & sub acute form of disease may
resolve by the avoidance of exposure. Corticosteroids are indicated
for the treatment of severe acute and sub-acute HP and for chronic HP that is
severe or progressive.

 

As our patient had small joint stiffness along with
positive Rheumatoid factor, Rheuma