Chapter 13: Mucocutaneous Fungal Infections

Candidiasis, caused primarily by Candida albicans and related species, develops opportunistically in individuals with compromised immunity, diabetes, or those receiving broad-spectrum antibiotics that disrupt normal flora. Clinical manifestations vary by location, including oral thrush with characteristic white plaques, vaginal candidiasis presenting with cottage-cheese discharge, cutaneous intertrigo in skin folds with satellite lesions, and paronychia around the nail beds. Diagnosis relies on microscopic identification of pseudohyphae through saline wet mount or potassium hydroxide examination, with topical antifungals serving as first-line therapy for most presentations and systemic fluconazole reserved for severe or recalcitrant cases. Dermatophytoses represent keratinolytic fungal infections caused by Trichophyton, Epidermophyton, and Microsporum species that spread through direct contact and fomites. These infections present distinctly by anatomical location: tinea capitis appears as patchy hair loss with black dot variants or inflammatory kerions in children, tinea corporis manifests as circular erythematous lesions with central clearing, tinea pedis presents as macerated interdigital skin or moccasin-type scaling, and tinea versicolor caused by Malassezia displays hypopigmented or hyperpigmented macules unaffected by sun exposure. While most dermatophytoses respond to topical azoles or allylamines, tinea capitis and onychomycosis require systemic oral antifungals because topical agents cannot adequately penetrate hair shafts and nail plates. Onychomycosis, typically caused by Trichophyton rubrum, affects toenails more frequently than fingernails and presents with thickened, discolored, brittle nails with possible separation from the nail bed. Critical to management is mandatory laboratory confirmation through fungal culture or PCR before initiating systemic therapy, given that only fifty to sixty percent of dystrophic nails result from fungal infection. The chapter emphasizes significant pharmacological considerations for systemic antifungal agents, including hepatotoxicity requiring baseline and periodic liver function monitoring, cytochrome P450-mediated drug interactions particularly with itraconazole, and contraindication in pregnancy due to teratogenic potential and possible contraceptive failure with griseofulvin.