Section 26: Fungal Infections of the Skin, Hair, and Nails

Introduction

• Superficial Fungal Infections. Caused by fungi that are capable of colonizing (cutaneous microbiome) and superficially invading skin and mucosal sites:

  • Candida species

  • Malassezia species

  • Dermatophytes.

• Deeper, Chronic Cutaneous Fungal Infections. Occur after percutaneous inoculation:

  • Phaeohyphomycosis (eumycetoma, chromoblastomycosis)

  • Sporotrichosis

• Systemic Fungal Infections with Cutaneous Dissemination. Occur most often with host defense defects. Primary lung infection disseminates hematogenously to multiple organ systems, including the skin: Cryptococcosis, histoplasmosis, North American blastomycosis, coccidioidomycosis, and penicillinosis.

Superficial Fungal Infections

ICD-9: 111 ○ ICD-10: B36

• Superficial fungal infections are the most common of all mucocutaneous infections, often caused by overgrowth of mucocutaneous microbiome.

• Candida Species. Require a warm humid microenvironment.

• Malassezia Species. Require a humid microenvironment and lipids for growth.

• Dermatophytes. Infect keratinized epithelium, hair follicles, and nail apparatus Trichosporon species Hortaea (Exophiala or Phaeoannellomyces) werneckii: Tinea nigra

Candidiasis

ICD-9: 112 ○ ICD-10: B37.0

• Etiology. Most commonly caused by the yeast Candida albicans. Less often by other Candida species.

Clinical Manifestation

Mucosal Candidiasis

Otherwise healthy individuals: oropharynx and genitalia. Host defense defects: in the esophagus and tracheobronchial tree.

Cutaneous Candidiasis

Intertriginous and occluded skin.

Disseminated Candidemia

Host defense defects, especially neutropenia. Usually after invasion of the gastrointestinal (GI) tract.

Epidemiology and Etiology

Etiology

C. albicans, C. tropicalis, C. parapsilosis, C. guilliermondii, C. krusei, C. pseudotropicalis, C. lusitaniae, C. glabrata.

Ecology

Candida spp. frequently colonize the GI tract and can be transmitted via the birth canal. Approximately 20% of healthy individals are colonized. Antibiotic therapy increases the incidence of colonization.

Ten percent of women are colonized vaginally; antibiotic therapy, pregnancy, oral contraception, and intrauterine devices increase incidence. C. albicans may transiently be present on the skin and infection is usually endogenous. Candida balanitis may be transmitted from sexual partner. The young and old are more likely to be colonized.

Host Factors

Host defense defects, diabetes mellitus, obesity; hyperhidrosis, warm climate, maceration; polyendocrinopathies; glucocorticoids; chronic debilitation.

Laboratory Examinations

Direct Microscopy

KOH preparation visualizes pseudohyphae and yeast forms (Fig. 26-1).

Culture

Identifies species of Candida; however, the presence in culture of C. albicans does not make the diagnosis of candidiasis. Sensitivities to antifungal agents can be performed on isolate in cases of recurrent infection. Rule out bacterial secondary infection.