Chronic Hypersensitivity Pneumonia

Figure 1. HRCT of Chronic HP

HRCT image from a patient with chronic HP shows bilateral inhomogeneous lung opacity consisting of areas of increased lung attenuation (ground-glass opacity and consolidation), decreased attenuation (mosaic perfusion), and normal lung parenchyma. This combination represents the "head-cheese" sign.

Note the presence of architectural distortion (interlobar fissure on the right) and traction bronchiectasis, indicating underlying fibrosis.

Figure 2. Head Cheese: The "head-cheese" sign (named for its resemblance to head cheese (image at right)) suggests the presence of a mixed restrictive and obstructive abnormality, and HP (image at left) is the most commonly imaged disorder that has this appearance.

The following images are from a biopsy of a patient with chronic HP caused by a pet dove.

Figure 3. Schaumann Body: Here, architectural distortion (enlargement of some air spaces and obliteration of others), interstitial fibrosis, and smooth muscle metaplasia are present.

schaumannsm

A lamellated, calcified body (Schaumann body) surrounded by remnants of a multinucleated giant cell is present near the center. A chronic inflammatory infiltrate is still present.

Find the Schaumann body surrounded by remnants of a giant cell.

Find an example of smooth muscle metaplasia.

Schaumann Bodies: Lamellated, calcified, Schaumann bodies develop within macrophages. As they enlarge, they may become extracellular. They may be associated in the macrophage with birefringent crystals of calcium oxalate (scroll down when you get there), which should not be mistaken for foreign material. Neither inclusion is specific for HP.

Figure 4. Honeycombing

Dilation of terminal bronchioles, respiratory bronchioles, and alveolar ducts caused by collapse and fibrosis of alveoli produces the honeycombing seen here. Lymphoid aggregates and scattered lymphoid cells are present in the surrounding interstitium. Histologically, chronic HP may not be able to be distinguished from other causes of end-stage fibrosis.

 

Note: The clinical diagnosis depends on the patient's history and other evidence of sensitivity to an antigen.

Return to Discussion--Chronic HP

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Schaumann body (lamellated calcospherite)

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Smooth muscle metaplasia

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