Medical mycoses can be divided into four categories: (1) cutaneous, (2) subcutaneous, (3) systemic, and (4) opportunistic. Some features of the important fungal diseases are described in Table 48–1. Cutaneous and subcutaneous mycoses are discussed in this chapter, and important features of the causative organisms are described in Table 48–2. The systemic and opportunistic mycoses are discussed in Chapters 49 and 50, respectively.
TABLE 48–1Features of Important Fungal Diseases |Favorite Table|Download (.pdf) TABLE 48–1 Features of Important Fungal Diseases
|Type ||Anatomic Location ||Representative Disease ||Genus of Causative Organism(s) ||Seriousness of Illness1 |
|Cutaneous ||Dead layer of skin ||Tinea versicolor ||Malassezia ||1+ |
| ||Epidermis, hair, nails ||Dermatophytosis (ringworm) ||Microsporum, Trichophyton, Epidermophyton ||2+ |
|Subcutaneous ||Subcutis ||Sporotrichosis ||Sporothrix ||2+ |
| || ||Mycetoma ||Several genera ||2+ |
|Systemic ||Internal organs ||Coccidioidomycosis ||Coccidioides ||4+ |
| || ||Histoplasmosis ||Histoplasma ||4+ |
| || ||Blastomycosis ||Blastomyces ||4+ |
| || ||Paracoccidioidomycosis ||Paracoccidioides ||4+ |
|Opportunistic ||Internal organs ||Cryptococcosis ||Cryptococcus ||4+ |
| || ||Candidiasis ||Candida ||2+ to 4+ |
| || ||Aspergillosis ||Aspergillus ||4+ |
| || ||Mucormycosis ||Mucor, Rhizopus ||4+ |
TABLE 48–2Important Features of Skin and Subcutaneous Fungal Diseases |Favorite Table|Download (.pdf) TABLE 48–2 Important Features of Skin and Subcutaneous Fungal Diseases
|Genus ||Forms in Tissue Seen by Microscopy ||Mode of Transmission ||Important Clinical Findings ||Laboratory Diagnosis |
|Trichophyton, Epidermophyton ||Hyphae ||Human to human ||Tinea capitis, tinea pedis, etc., “ringworm” Ring of inflammatory, pruritic vesicles with a healing center ||Potassium hydroxide (KOH) prep shows septate hyphae culture on Sabouraud’s agar |
|Microsporum ||Hyphae ||Animal to human as well as human to human ||Tinea capitis, tinea pedis, etc., “ringworm” Ring of inflammatory, pruritic vesicles with a healing center ||KOH prep shows septate hyphae culture on Sabouraud’s agar |
|Malassezia ||Hyphae and yeasts ||Human to human ||Scaly plaques on trunk; often hypopigmented; often nonpruritic ||KOH prep shows mixture of hyphae and yeasts |
|Sporothrix ||Yeasts ||Penetrating lesion in garden implants fungal spores, e.g., rose thorn ||Pustule or ulcer on hands often with nodules on arms ||KOH prep shows cigar-shaped yeasts culture at 20°C shows hyphae with daisy-like conidia |
Dermatophytoses are caused by fungi (dermatophytes) that infect only superficial keratinized structures (skin, hair, and nails), not deeper tissues. The most important dermatophytes are classified in three genera: Trichophyton, Epidermophyton, and Microsporum. They are spread from infected persons by direct contact. Microsporum is also spread from animals such as dogs and cats. This indicates that to prevent reinfection, the animal must be treated also.
Dermatophytoses (tinea, ringworm) are chronic infections often located in the warm, humid areas of the body (e.g., athlete’s foot and ...