Dermatophytosis differential diagnosis
Overview
Dermatophytosis should be differentiated from other conditions
Differential Diagnosis
Dermatophytoses should be differentiated from other superficial skin infections which may all present as a red, pruritic, annular and scaly rash on different parts of the body. Tinea corporis should also be differentiated from other annular skin eruptions, especially subacute cutaneous lupus erythematosus (SCLE), granuloma annulare, and erythema annulare centrifugum.
Differential diagnoses of red, pruritic, annular, scaly rash
| Name of superficial infection | Clinical presentation | Extension to hair follicle | Fungus(i) | Systemic disease | KOH preparations | Morphology in tissue sections |
|---|---|---|---|---|---|---|
| Tinea or ringworm, followed by the location in the body | Round lesions with scaly border, accompanied by pruritus and burning | Yes; when suppurative known as kerion, when chronic known as Majocchi's granuloma | Dermatophytes (Epidermophyton spp., Trichophytum spp., Microsporum spp.) | Very rare but can invade the dermis and soft tissues, causing mycetomas | Hyphae with or without septations | Hyphae cannot be visualized in the keratin with H&E, special stains are needed |
| Tinea versicolor | Hypo and hyperpigmentation in patients with oily and sweaty skin, fine scales when scratching | Yes, known as Pityrosporum folliculits | Malassezia spp. | Systemic infections may occur in premature neonates receiving parenteral nutrition and in other immunosuppressed hosts | Yeasts and hyphae (“spaghetti and meat balls”) | Faintly basophilic hyphae in the stratum corneum |
| Tinea nigra | Brown to black macule, usually in palms, with some scaling | No | Phaeoannellomyces werneckii | Not described | Darkly pigmented, septated, and branching hyphae | Pigmented hyphae in the stratum corneum |
| White piedra | Creamy-white, small, soft nodules in hair shafts | No | Trichosporon spp. | Immunosuppressed patients may have lung infiltrates, renal involvement, and fungemia | Septate hyphae perpendicular to hair shaft | Not used for diagnosis |
| Black piedra | Hard dark nodules in hair shafts | No | Piedraia hortae | Not described | Collections of crescent ascospores surrounded by pigmented hyphae | Not used for diagnosis |
| Superficial candidiasis | Intertrigo, chronic paronychia, onychodystrophy, cheilitis | Yes | Candida spp. | Yes, particularly in patients with AIDS and depending on the level of immunosuppression | Yeasts, pseudohyphae may be observed | Fungal elements may be seen through the biopsy, vascular invasion must be determined |
Differential diagnoses of annular skin lesions
| Tinea corporis | Scaly, annular, erythematous plaques or papules on glabrous skin | Topical and systemic antifungals |
| Pityriasis rosea | Small, fawn-colored, oval patches with fine scale along the borders, following skin cleavage lines | Topical and systemic corticosteroids; UVA, UVB |
| Granuloma annulare | Indurated, nonscaly, skin-colored annular plaques and papules, usually on the extremities | Topical and intralesional corticosteroids |
| Sarcoidosis | Indurated, erythematous plaques | Topical, intralesional and systemic corticosteroids; antimalarials; thalidomide |
| Hansen's disease | Erythematous annular plaques, with or without scale | Dapsone; rifampin (Rifadin) |
| Urticaria | Evanescent annular, nonscaly, erythematous plaques | Oral antihistamines |
| Subacute cutaneous lupus erythematosus | Annular or papulosquamous plaques, with or without scale, on sun-exposed areas | Topical, intralesional and systemic corticosteroids; antimalarials |
| Erythema annulare centrifugum | Annular patches with trailing scale inside erythematous borders | Topical and systemic corticosteroids; oral antihistamines; treatment of the underlying cause |
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