Dermatophytosis
Dermatophytosis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Dermatophytosis, commonly called tinea, may affect the scalp (tinea capitis), body (tinea corporis), nails (tinea unguium), hands (tinea manuum), feet (tinea pedis), groin (tinea cruris), and bearded skin (tinea barbae). With effective treatment, the cure rate is very high, although about 20% of infected people develop chronic conditions.
Causes and incidence
Tinea infections (except for tinea versicolor) result from dermatophytes (fungi) of the genera Trichophyton, Microsporum, and Epidermophyton. Transmission can occur through contact with infected lesions, household cats and dogs, and soiled or contaminated articles, such as shoes, towels, or shower stalls.
Tinea infections are prevalent in the United States. They’re more common in males than in females.
Signs and symptoms
Lesions vary in appearance depending on the site of invasion (inside or outside the hair shaft), duration of infection, level of host resistance, and amount of inflammatory response. Tinea capitis ranges in appearance from broken-off hairs with little scaling to severe painful, inflammatory, pus-filled masses (kerions) covering the entire scalp. Partial hair loss occurs in all cases. The cardinal clue is broken-off hairs.
Tinea corporis produces flat lesions on the skin at any site except the scalp, bearded skin, hands, or feet. These lesions may be dry and scaly or moist and crusty; as they enlarge, their centers heal, causing the classic ring-shaped appearance. In tinea unguium (onychomycosis), infection typically starts at the tip of one or more toenails (fingernail infection is less common) and produces gradual thickening, discoloration, and crumbling of the nail, with accumulation of subungual debris. Eventually, the nail may be destroyed completely.
Tinea pedis, or athlete’s foot, causes scaling and blisters between the toes. Severe infection may result in inflammation, with severe itching and pain on walking. A dry, squamous inflammation may affect the entire sole. (See Athlete’s foot, page 1240.) Tinea manuum produces scaling patches and hyperkeratosis on the palmar surface. It’s usually unilateral and associated with tinea pedis. Tinea cruris (jock itch) produces red, raised, sharply defined, itchy or burning lesions in the groin that may extend to the buttocks, inner thighs, and the external genitalia. Warm weather, obesity, and tight clothing encourage fungus growth. Tinea barbae is an uncommon infection that affects the bearded facial area of men.
Diagnosis
CONFIRMING DIAGNOSIS Microscopic examination of lesion scrapings prepared in potassium hydroxide solution will reveal branching fungal hyphae. Gently heating the slide helps separate epithelial cells and hyphae. Lowering the microscope condenser and dimming the light make hyphae easier to identify, as does adding a drop of ink to the potassium hydroxide.
Other diagnostic procedures include Wood’s light examination (useful in only about 5% of cases of tinea capitis) and culture of the infecting organism, which is important for identifying hair and nail fungal infections.
Treatment
Tinea infections respond to a wide variety of medications. Typically, infections of the skin (hands, body, feet, and groin) require only topical therapy. Infections of the hair and nails, skin infections causing chronic thickening of the skin, and other unresolving infections require oral antifungal therapy.
Topical preparations are commonly azole-based, though other preparations are available. Oral therapy includes azole-based medications and terbinafine. Griseofulvin is falling out of favor because newer products are easier to use and have a shorter duration of therapy.
Alert Caution must be taken when using systemic antifungals: liver enzyme levels must be monitored before and throughout treatment if therapy is expected to extend more than 2 months, and chronic medications must be monitored because of the antifungal’s potential effect on blood levels.
Treatment should continue from several days to 2 weeks after lesions have resolved. Topical agents with soothing and cooling effects may be used with systemic therapy for infections with severe itching and burning; they may be discontinued when the immediate discomfort resolves.
Special considerations
Management of tinea infections requires medication compliance, observation for sensitivity reactions, observation for secondary bacterial infections, and patient teaching. Specific care varies by site of infection:
❑ For tinea barbae: Suggest that the patient let his beard grow (whiskers may be trimmed with scissors, not a razor). If the patient insists that he must shave, advise him to use an electric razor instead of a blade.
❑ For tinea capitis: If the condition worsens, discontinue medications and notify the physician. Use good hand-washing technique, and teach the patient to do the same. Spores of tinea capitis are shed in the air around an infected patient or may spread on contaminated clothing and other personal articles. To prevent spread of infection to others, advise him to wash his towels, bedclothes, and combs frequently in hot water and to avoid sharing them. Suggest that family members be checked for tinea capitis.
❑ For tinea corporis: Use abdominal pads between skin folds for the patient with excessive abdominal girth; change pads frequently. Check the patient daily for excoriated, newly denuded areas of skin. Apply wet Burow’s compresses two or three times daily to decrease inflammation and help remove scales.
❑ For tinea cruris: Instruct the patient to dry the affected area thoroughly after bathing and to evenly apply antifungal powder after applying the topical antifungal agent. Advise him to wear loose-fitting clothing, which should be changed frequently and washed in hot water.
❑ For tinea pedis: Encourage the patient to expose his feet to air whenever possible, and to wear sandals or leather shoes and clean, white cotton socks. Instruct the patient to wash his feet twice daily and, after drying them thoroughly, to apply antifungal cream followed by antifungal powder to absorb perspiration and prevent excoriation. Tell him to allow his shoes to dry out by alternating pairs every other daily. Also tell him to wear shower shoes when using public facilities.
❑ For tinea unguium: Keep nails short and straight. Gently remove debris under the nails with an emery board. Prepare the patient for prolonged therapy.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Tinea versicolor (Professional Guide to Diseases (Eighth Edition))
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