Hyalohyphomyces

Hyaline Hyphomyces: General Considerations

Three broad groups can help organize this "garbage can" category:

Conidia formed in chains (Aspergillus, Penicillium, Paecilomyces, Scopulariopsis)
Conidia formed in clusters (Acremonium, Fusarium, Gliocladium, Trichoderma)
Conidia borne singly (Beauveria, Pseudallescheria boydii/Scedosporium apiospermum)

These fungi share colorless, septate hyphae that are generally more slender than those of the Zygomycetes. Colony color varies widely, but the reverse is white or light-colored.

Hyaline Hyphomyces: Direct Examination

Hyphae are regular, 3-6μ, with parallel walls, irregular branching, and septae
Hyaline (colorless) appearance when unstained

Figure 1 below shows an H&E stained section of lung; on the right is respiratory epithelium and underlying chronic inflammation. On the left is a so-called "fungus ball" or aspergilloma. Figure 2 shows a special silver stain designed to highlight fungal cell walls in tissue sections. Figure 3 shows an unfixed, deflated section of lung containing an aspergilloma.

FIG. 1. This is a low power photomicrograph of an H&E stained section of lung. The fungus ball or aspergilloma on the left is composed almost entirely of matted fungal hyphae.

FIG. 2. This is a Gomori methenamine silver nitrate stained section of the aspergilloma shown above.

FIG. 3. This is a cross-section of lung containing a small aspergilloma (arrow). Histologic examination showed the features seen in figures 1 and 2.

Since the hyaline hyphomyces constitute such a large group, they will be considered according to the arrangement of their conidia. Aspergillus, a member of the group of hyalohyphomyces that forms conidia in chains will be considered separately because of its importance as both a pathogen and a contaminant.

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