Chapter 053. Eczema and Dermatitis (Part 10) Ecthyma is a variant of impetigo that causes punched-out ulcerative lesions. It may result from neglected or inadequately treated impetigo. Treatment of both ecthyma and impetigo involves gentle debridement of adherent crusts, which is facilitated by the use of soaks and topical antibiotics, in conjunction with appropriate oral antibiotics. Furunculosis is also caused by S. aureus, and this disorder has gained prominence in the last decade because of CA-MRSA. A furuncle, or boil, is a painful, erythematous, nodule that can occur on any cutaneous surface. The lesions may be solitary but are most often multiple. Patients frequently believe they have been bitten by spiders or insects. Family members or close contacts may also be affected. Furuncles can rupture and drain spontaneously or may need incision and drainage, which may be adequate therapy for small solitary furuncles without cellulitis or systemic symptoms. Whenever possible, lesional material should be sent for culture. Current recommendations for methicillin-sensitive infections are β-lactam antibiotics. Therapy for CA-MRSA was discussed previously (see "Atopic Dermatitis"). Warm compresses and nasal mupirocin are helpful therapeutic additions. Severe infections may require IV antibiotics. Table 53-5 Common Skin Infections Clinical Features Etiologic Agent Treatmen t Impetigo Honey- colored crusted papules, plaques, or bullae Group A Streptococcus and Staphylococcus aureus Systemic or topical antistaphylococc al antibiotics Dermatophytos is Inflammatory or noninflammatory annular scaly plaques; may have hair loss; groin involvement Trichophyto n, Epidermophyton, or Microsporum Topical azoles, systemic griseofulvin, terbinafine, or spares scrotum; hyphae on KOH preparation sp. azoles Candidiasis Inflammatory papules and plaques with satellite pustules, frequently in intertriginous areas; may involve scrotum; pseudohyphae on KOH preparation Candida albicans and other Candida species Topical nystatin or azole s; systemic azoles for resistant disease Tinea versicolor Hyperpigment ed or hypopigmented scaly patches on the trunk; characteristic mixture of hyphae and spores on KOH preparation ("spaghetti and Malassezia furfur Topical selenium sulfide lotion or azoles meatballs") Erysipelas and Cellulitis See Chap. 119 Dermatophytosis Dermatophytes are fungi that infect skin, hair, and nails and include members of the genera Trichophyton, Microsporum, and Epidermophyton. Tinea corporis, or infection of the relatively hairless skin of the body (glabrous skin), may have a variable appearance depending on the extent of the associated inflammatory reaction (see Fig. 52-11). Typical infections have an annular appearance that patients refer to as "ringworm." Deep inflammatory nodules or granulomas occur in some infections—especially in those infections inappropriately treated with mid- to high-potency topical glucocorticoids. Involvement of the groin (tinea cruris) is more common in males than females. It presents as a scaling, erythematous eruption sparing the scrotum. Infection of the foot (tinea pedis) is the most common dermatophyte infection and is often chronic; it is characterized by variable erythema, edema, scaling, pruritus, and occasionally vesiculation. Involvement may be widespread or localized but generally involves the web space between the fourth and fifth toes. Infection of the nails (tinea unguium or onychomycosis) occurs in many patients with tinea pedis and is characterized by opacified, thickened nails and subungual debris. The distal-lateral variant is most common. Proximal subungual onychomycosis may be a marker for HIV infection or other immunocompromised states. Dermatophyte infection of the scalp (tinea capitis) has returned in epidemic proportions, particularly affecting inner-city children, but it also affects adults. The predominant organism is T. tonsurans, which can produce a relatively noninflammatory infection with mild scale and hair loss that is diffuse or localized. T. tonsurans can also cause a markedly inflammatory dermatosis with edema and nodules. This latter presentation is a kerion. The diagnosis of tinea can be made from skin scrapings, nail scrapings, or hair by culture or direct microscopic examination with potassium hydroxide (KOH). Nail clippings may be sent for histologic examination with periodic acid Schiff (PAS) stain. . Chapter 053. Eczema and Dermatitis (Part 10) Ecthyma is a variant of impetigo that causes punched-out ulcerative. azoles Candidiasis Inflammatory papules and plaques with satellite pustules, frequently in intertriginous areas; may involve scrotum; pseudohyphae on KOH preparation Candida albicans and. characteristic mixture of hyphae and spores on KOH preparation ("spaghetti and Malassezia furfur Topical selenium sulfide lotion or azoles meatballs") Erysipelas and Cellulitis See Chap.