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Chapter 48: Cutaneous & Subcutaneous Mycoses

INTRODUCTION

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
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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+

11+ = not serious, treatment may or may not be given; 2+ = moderately serious, treatment often given; 4+ = serious, treatment given especially in disseminated disease.

Table 48–2Important Features of Skin and Subcutaneous Fungal Diseases
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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

Additional information regarding the clinical aspects of infections caused by the fungi in this chapter is provided in Part IX entitled Infectious Diseases beginning on Chapter 70.

CUTANEOUS MYCOSES

Dermatophytoses

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 to three genera: Trichophyton, Epidermophyton, and Microsporum. All of these dermatophytes are molds. They are not dimorphic.

The dermatophytes are spread from person-to-person by direct contact. Microsporum is also spread from animals such as dogs and cats. This indicates that to prevent reinfection by Microsporum...

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