Chronic hypersensitivity pneumonitis (historical)
Updates to Article Attributes
Chronic hypersensitivity pneumonitis (CHP) refers to hypersensitivity pneumonitis where there is radiological evidence of fibrosis and represents the end-stage of repeated or persistent pneumonitis 7.
Radiographic features
CT
High-resolution CT of the chest typically reveals indistinct centrilobular peribronchiolar nodular opacities - micronodules) of varying numbers 5. Other features include:
- ground-glass opacities
- lobular areas of hyperlucency (mosaic perfusion) caused by bronchiole obstruction
- areas of pulmonary fibrosis and honeycombing
There is often a middle or lowerupper zone predominance of CT findings with sparing of the lung bases, unlike non-specific interstitial pneumonia (NSIP) or usual interstitial pneumonia (UIP), which show a lower zone predominance.
The presence of an extensive reticular pattern, traction bronchiectasis, and honeycombing have been shown to closely correlate with the presence of histologic fibrosis in chronic hypersensitivity pneumonitis 6.
Treatment and prognosis
The presence of fibrotic changes confers a poor prognosis.
Differential diagnosis
In some cases, it may be difficult to differentiate from idiopathic pulmonary fibrosis - UIP cases are also thought to have honeycombing and peripheral or lower lung zone predominance of disease, and less likely to have micronodules 4.
Sometimes some forms of advanced-stage sarcoidosis may carry some imaging overlap 8.
-</ul><p>There is often a middle or lower zone predominance of CT findings with sparing of the lung bases, unlike <a href="/articles/non-specific-interstitial-pneumonia-1">non-specific interstitial pneumonia (NSIP)</a> or <a href="/articles/usual-interstitial-pneumonia">usual interstitial pneumonia (UIP)</a>, which show a lower zone predominance.</p><p>The presence of an extensive reticular pattern, <a href="/articles/traction-bronchiectasis">traction bronchiectasis</a>, and <a href="/articles/honeycombing-lungs">honeycombing</a> have been shown to closely correlate with the presence of histologic fibrosis in chronic hypersensitivity pneumonitis <sup>6</sup>.</p><h4>Treatment and prognosis</h4><p>The presence of fibrotic changes confers a poor prognosis.</p><h4>Differential diagnosis</h4><p>In some cases, it may be difficult to differentiate from <a href="/articles/idiopathic-pulmonary-fibrosis">idiopathic pulmonary fibrosis</a> - UIP cases are also thought to have honeycombing and peripheral or lower lung zone predominance of disease, and less likely to have micronodules <sup>4</sup>.</p><p>Sometimes some forms of advanced-stage sarcoidosis may carry some imaging overlap <sup>8</sup>.</p>- +</ul><p>There is often a middle or upper zone predominance of CT findings with sparing of the lung bases, unlike <a href="/articles/non-specific-interstitial-pneumonia-1">non-specific interstitial pneumonia (NSIP)</a> or <a href="/articles/usual-interstitial-pneumonia">usual interstitial pneumonia (UIP)</a>, which show a lower zone predominance.</p><p>The presence of an extensive reticular pattern, <a href="/articles/traction-bronchiectasis">traction bronchiectasis</a>, and <a href="/articles/honeycombing-lungs">honeycombing</a> have been shown to closely correlate with the presence of histologic fibrosis in chronic hypersensitivity pneumonitis <sup>6</sup>.</p><h4>Treatment and prognosis</h4><p>The presence of fibrotic changes confers a poor prognosis.</p><h4>Differential diagnosis</h4><p>In some cases, it may be difficult to differentiate from <a href="/articles/idiopathic-pulmonary-fibrosis">idiopathic pulmonary fibrosis</a> - UIP cases are also thought to have honeycombing and peripheral or lower lung zone predominance of disease, and less likely to have micronodules <sup>4</sup>.</p>
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