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Fungi are an important cause of dermatological disease.
Visit: Cutaneous Infections and Infestations
Fungal identification:
The PAS stain, sometimes combined with diastase digestion, is most frequestly used. It stains the cell walls of fungi a purple colour of varying intensity.
The silver methenamine stain, usually Grocott’s modification, is a reliable method of detecting fungi: it stains them black against a green background.
It is more reliable than the PAS stain for detecting degenerate fungal elements and the rare animal pathogens among the aquatic fungi, although it may be less reliable with zygomycetes.
Cryptococcus neoformans may be stained with the mucicarmine stain or a combined alcian blue-PAS stain, which shows the cell wall and capsule in contrasting colors. It is usually doubly refractile under polarized light.
Calcoflour white can be used to stain frozen or paraffin sections as well as tissue smears.
The sections must be viewed with a fluorescence microscope.
Certain fungi are even autoflourescent when a section stained with hematoxylin and eosin is exposed to ultraviolet light.
These include Blastomyces , Cryptococcus , Candida , Aspergillus , Coccidioides and occasionally Histoplasma .
Polymerase chain reaction PCR)-based techniques are now being used to identify specific species of fungi, including dermatophytes.
Superficial filamentous infections:
Yeast infections:
Pityriasis versicolor
Pityrosporum folliculitis
Trichosporonosis and
white piedra
Systemic mycoses:
Infection by dematiaceous fungi:
Tinea nigra
Mycetoma & morphologically similar conditions:
Zygomycoses:
Hyalohyphomycoses:
Miscellaneous mycoses:
Keloidal blastomycosis
(Lobo’s disease)
Algal infections:
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