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Emergency and Acute Medicine – Tinea Infections (Cutaneous)
Cutaneous tinea infections are superficial fungal infections involving the hair, skin, or nails, typically confined to the stratum corneum. They are among the most common diseases worldwide and require keratin for growth, which explains why mucosal surfaces are not affected. These infections are named according to their anatomical location. The causative organisms are dermatophytes, primarily species of Microsporum, Trichophyton, and Epidermophyton. In contrast, tinea versicolor is caused by Malassezia furfur, a yeast, and is not a true dermatophyte infection. Transmission may occur via direct contact with infected individuals, animals, or contaminated soil, and skin trauma or maceration facilitates fungal entry. In children, spread can occur through shared items such as toys or brushes, while nail infections are uncommon unless associated with conditions like immunosuppression or Down syndrome.
Clinical presentation varies depending on the site of infection but is generally characterized by itching as the main symptom. Tinea capitis primarily affects children and presents with scalp involvement, including alopecia, scaling, and characteristic “black dots” from broken hairs. Inflammatory forms such as kerion may appear as boggy, purulent masses with associated lymphadenopathy. Tinea corporis, or ringworm, presents as annular lesions with raised, well-demarcated borders and central clearing, commonly affecting the trunk and extremities. Tinea cruris involves the groin, thighs, and buttocks, producing erythematous, scaly patches that typically spare the scrotum and penis, helping differentiate it from candidiasis. Tinea pedis, the most common form in adults, manifests as scaling, maceration, and fissuring between the toes, often associated with moisture and poor foot hygiene. Tinea unguium (onychomycosis) causes thickened, discolored nails with subungual debris and nail separation. Tinea versicolor presents with hypo- or hyperpigmented macules on the upper trunk, arms, and neck, especially in warm climates.
Diagnosis is primarily clinical, based on history and physical examination. If uncertainty exists, confirmation can be achieved through microscopy using potassium hydroxide (KOH) preparation, which demonstrates fungal elements such as septate hyphae in dermatophyte infections or the characteristic “spaghetti and meatballs” pattern in Malassezia. Fungal cultures are generally not necessary due to slow growth. Wood lamp examination has limited utility, as most dermatophytes do not fluoresce, although Microsporum species may appear green and Malassezia yellow-green.
Treatment depends on the site and severity of infection. Most superficial infections such as tinea corporis, cruris, and pedis respond well to topical antifungals, including terbinafine or imidazoles like clotrimazole and miconazole. Keeping the affected area dry and maintaining hygiene are important adjuncts. In contrast, infections involving hair or nails, such as tinea capitis and tinea unguium, require systemic therapy because topical agents do not adequately penetrate these structures. Oral terbinafine is commonly used and is considered first-line for tinea capitis, while longer treatment durations are required for nail infections. Selenium sulfide or ketoconazole shampoos may reduce transmission in scalp infections. Tinea versicolor is typically treated with topical agents such as selenium sulfide shampoo or topical azoles, with oral therapy reserved for extensive or refractory cases.
Most patients improve within 1–2 weeks of treatment, although hair and nail infections require prolonged therapy lasting several months. Patients can usually be managed as outpatients, with hospital admission reserved for rare cases of invasive infection in immunocompromised individuals or complicated kerion with secondary bacterial infection. Follow-up is important for patients on oral antifungal therapy to monitor for adverse effects, particularly hepatotoxicity.
Key clinical pearls include recognizing tinea capitis as the most common dermatophyte infection in children and understanding that itching is the predominant symptom across most forms. Tinea pedis can predispose to cellulitis, and recurrence of infections, particularly in the feet and groin, is common. Preventive measures such as proper hygiene and avoiding sharing personal items are essential to reduce reinfection and transmission.
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