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 penicilliosis.

SUPERFICIAL FUNGAL INFECTIONS ICD-10: B36

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

• Candida Species. Require a warm humid environment.

• Malassezia Species. Require lipids for growth.

• Dermatophytes. Infect keratinized epithelium, hair follicles, and nail apparatus. Trichophyton, Microsporum, and Epidermophyton species.

• Hortaea werneckii. Causes tinea nigra.

CANDIDIASIS 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 occur 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. guilliermondi, Candida krusei, C. kefyr, C. zeylanoides, C. glabrata.

ECOLOGY Candida spp. frequently colonize the GI tract and can be transmitted via the birth canal. Approximately 20% of healthy individuals 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, and obesity; hyperhidrosis, warm climate, and 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 the culture of C. albicans does not make the diagnosis of candidiasis. Sensitivities to antifungal agents can be performed on isolated cases of recurrent infection. Rule out bacterial secondary infection.

CUTANEOUS CANDIDIASIS

• Cutaneous candidiasis occurs in moist, occluded sites.

• Many patients have predisposing factors.

See Section 32 for candidiasis of the nail.

Clinical ...