Hypersensitivity Pneumonia (HP)

Introduction: Common known causes of HP are S. rectivirgula (formerly called M. faeni) (farmer's lung) and avian proteins (pigeon breeder's lung). A few reports of a similar disease caused by aspergillus are summarized below.

Case reports: Riddle et al. described a case of HP in a maltworker, who was sensitized to A. clavatus. Moldy barley was the source. The diagnosis was supported by the clinical story, the presence of precipitating antibodies in the serum, a late reaction to intradermal injection of antigen, and a positive inhalation provocation test [1].

In another report, a 37-year-old woman developed several episodes of HP after bagging moldy oats. An intradermal test with A. fumigatus was positive at 48 h, but not at 8 h. Precipitins to aspergillus antigens were present, and blood lymphocytes showed transformation after exposure to aspergillus antigen. However, the histology from a transbronchial biopsy showed granulomas with purulent centers that contained hyphal fungi [2]. These granulomas differ from those of the usual, non-necrotizing granuloma of HP. They resemble those of chronic granulomatous disease, which was not excluded in this case.

A 20-year-old man exposed to vegetable compost developed two episodes of HP. Serum precipitins were positive for A. fumigatus. The second episode responded to prednisone, but 2 weeks after symptoms began, he developed invasive disease, which responded to amphotericin and flucytosine [3].

A recent report described typical HP in 5 patients who processed esparto grass for use in woven and construction materials [4]. Although A. fumigatus was the only agent that could be isolated from the grass, patients also had antibody to T. vulgaris and M. faeni. Inhalational challenge with an extract of grass produced symptoms in all 5, but challenge with aspergillus antigens alone was not performed. Lavage fluid showed a lymphocytosis with CD8 T-cell predominance, and transbronchial biopsies showed a lymphocyte infiltrate in all and granulomas in one.

References

1. Riddle H, Channell S, Blyth W, Weir D, Lloyd M, Amos W, Grant I. Allergic alveolitis in a maltworker. Thorax 1968; 23:271-280.

2. Yocum M, Saltzman A, Strong D, Donaldson J, Ward G Jr, Walsh F, Cobb O Jr, Elliott R. Extrinsic allergic alveolitis after Aspergillus fumigatus inhalation. Evidence of a type IV immunologic pathogenesis. Am J Med 1976; 61:939-945.

3. Vincken W, Roels P. Hypersensitivity pneumonitis due to Aspergillus fumigatus in compost. Thorax 1984; 39:74-5.

4. Hinojosa M, Fraj J, De la Hoz B, Alcazar R, Sueiro A. Hypersensitivity pneumonitis in workers exposed to esparto grass (Stipa tenacissima) fibers. J Allergy Clin Immunol. 1996; 98:985-91.

Clinical summaryDiscussion

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