Dermatology, Venereology and Leprosy
Superficial Fungal Infections
Fungal skin infections for MBBS and NEET-PG: dermatophytes and tinea, KOH mount, pityriasis versicolor, candidiasis, and topical versus systemic antifungals, mapped to NMC codes DR7.
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Superficial Fungal Infections
Fungal skin infections for MBBS and NEET-PG: dermatophytes and tinea, KOH mount, pityriasis versicolor, candidiasis, and topical versus systemic antifungals, mapped to NMC codes DR7.
Superficial fungal infections span the dermatophytoses, pityriasis versicolor and candidiasis. This chapter covers the recognition of ringworm and its site-specific names, the potassium hydroxide mount and Wood's lamp, the yeast infections, and the choice between topical and systemic antifungals, including why hair and nail disease needs oral treatment.
High-yield: Superficial Fungal Infections
- Dermatophytes are the fungi that cause ringworm and belong to three genera: Trichophyton, Microsporum and Epidermophyton.
- Dermatophytoses are named by site: tinea capitis (scalp), corporis (body), cruris (groin), pedis (foot), unguium (nail) and faciei (face).
- The classic tinea lesion is an annular scaly plaque with a raised active edge and central clearing, hence the name ringworm.
- A potassium hydroxide mount of skin scrapings shows branching septate hyphae and is the key bedside test for dermatophytes.
- Tinea capitis is a childhood infection, and some Microsporum species fluoresce green under Wood's lamp while Trichophyton species do not.
- A kerion is a boggy inflammatory mass of tinea capitis representing a strong host response and can lead to scarring alopecia.
- Pityriasis versicolor is caused by Malassezia and gives hypopigmented or hyperpigmented scaly macules on the trunk with a spaghetti and meatballs pattern on microscopy.
- Candidal intertrigo produces moist erythema in skin folds with characteristic satellite pustules beyond the main patch.
- Oral candidiasis or thrush appears as removable white plaques and, in an adult without obvious cause, should prompt a search for immunosuppression.
- Predisposing factors for candidiasis include diabetes, moisture, obesity, broad-spectrum antibiotics and immunosuppression.
- Topical azoles and terbinafine are effective for most limited dermatophyte and candidal infections.
- Tinea capitis and tinea unguium need systemic antifungals such as terbinafine or itraconazole because topical agents do not penetrate hair and nail adequately.
- Griseofulvin remains a useful oral agent for tinea capitis, particularly in children.
- Irrational use of combination creams containing potent steroids is driving widespread, difficult-to-treat and recurrent dermatophytosis in India.
Superficial mycoses
- **Dermatophytes:** Trichophyton, Microsporum, Epidermophyton. Annular scaly plaque, KOH shows hyphae.
- **Pityriasis versicolor:** Malassezia. Pale or dark scaly trunk macules, spaghetti and meatballs on KOH.
- **Candidiasis:** Moist folds with satellite pustules; diabetes, antibiotics, immunosuppression.
- **Systemic therapy:** Tinea capitis and tinea unguium need oral terbinafine, itraconazole or griseofulvin.
NMC competencies in this chapter
- **DR7.1:** Aetiology, microbiology, pathogenesis and clinical features of fungal infections
- **DR7.2:** Identifying Candida species in fungal scrapings and KOH mount
- **DR7.3:** Pharmacology and action of topical and systemic antifungal agents
Frequently Asked Questions
How is a dermatophyte infection confirmed at the bedside?
By a potassium hydroxide mount of skin scrapings from the active edge, which dissolves keratin and reveals branching septate fungal hyphae under the microscope.
Why do nail and scalp fungal infections need oral treatment?
Topical antifungals cannot penetrate the nail plate or hair follicle adequately, so tinea unguium and tinea capitis require systemic agents such as terbinafine, itraconazole or griseofulvin.
What is pityriasis versicolor?
A superficial yeast infection caused by Malassezia that produces pale or dark finely scaly macules on the trunk, with a characteristic spaghetti and meatballs appearance on microscopy.
What suggests candidal rather than dermatophyte infection in a fold?
Candidal intertrigo shows moist erythema with satellite pustules beyond the main patch and is favoured by diabetes, moisture, obesity, antibiotics and immunosuppression.
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