Dermatomycosis( ( 真菌性皮肤病 ) 浙医一院皮肤科

Transcription

1 Dermatomycosis( ( 真菌性皮肤病 ) 浙医一院皮肤科 方红 Dermatophytosis is a superficial infection of the skin, hair and/or nails by fungi classified as dermatophytes. The dermatophytoses are some of the most common diseases of man. The incidences of infection vary greatly, at least 10%~20% of the world s population may be infected with these organisms. Dermatomycosis can be divided into superficial and deep mycoses. Approximately 25 species of dermatophytes infect human. Three anamorphic genera cause dermatophytosis. dermatophytes( 皮肤癣菌 ) Trichophyton ( 毛癣菌属 ) Microsporium( 小孢子菌属 ) Epidermophyton ( 表皮癣菌属 ) The dermatophytoses can be transmitted from human to human (anthropophilic), from animal to human (zoophilic) or from the soil(geophilic). Diagnosis The diagnosis of suspected tinea infection is made by microscopic direct examination and/or culture of fungi. Direct examination of fungi Removed skin, hair or nails from the infected area and place the sample on a microscope slide to which 1-2 drops of 10% or 20% of potassium hydroxide (KOH) are added. Place a cover-slide on the preparation and heated slightly. Examine under the microscope. Culture A culture using Sabouraud s agar supplemented with antibiotics may be useful to identify the fungus responsible for the infection. Tinea capitis( 头癣 ) Tinea capitis, predominantly a disease of preadolescent children, is a dermatophytic trichomycosis of the scalp. Clinical presentations vary widely, ranging from mild scaling and broken-off hairs to severe, painful inflammation with painful, boggy nodules that drain pus and result in scarring alopecia. Synonyms: Ringworm of the scalp, tinea tonsurans. Epidemiology and Etiology Age of Onset Toddlers and school-age children. Most common at 6 to 10 years of age; less common after age 16. In adults it occurs most commonly in a rural setting. Etiology/Demography 90% of cases of tinea capitis caused by M. canis.t. tonsurans and T.violaceum commonly. Classification Tinea alba : Fine scaling with fairly sharp margin. Hair shaft becomes brittle, breaking off at or slightly above scalp. Small patches coalesce, forming larger patches. Inflammatory response

2 minimal, but massive scaling. Several or many patches, randomly arranged may be present. M. canis( 犬小孢子菌 ), T.mentagrophytes( 须癣毛癣菌 ),and M. ferrugineum, infections show bright green fluorescence with Wood's lamp. Favus: Early cases show perifollicular erythema and matting of hair. Later, thick yellow adherent crusts (scutula) composed of skin debris and hyphae that are pierced by remaining hair shafts. Fetid odor. In treatment, cutaneous atrophy, scar formation, and scarring alopecia. Caused by T. schoenleinii. Shows dim green fluorescence with Wood's lamp. little tendency to clear spontaneously. Black-dot tinea: Broken-off hairs near surface give appearance of dots (swollen hair shafts) in dark-haired patients. Dots occur as affected hair breaks at surface of scalp. Tends to be diffuse and poorly circumscribed. Low-grade folliculitis may be present. Resembles seborrheic dermatitis, chronic cutaneous lupus erythematosus. Usually caused by T. violaceum andt. Tonsurans. Shows not fluorescence with Wood's lamp. Kerion: Inflammatory mass in which remaining hairs are loose. Characterized by boggy, purulent, inflamed nodules and plaques. Usually extremely painful; drains pus from multiple openings, like honeycomb. Hairs do not break off but fall out and can be pulled without pain. Follicles may discharge pus; sinus formation; mycetoma like grains. Thick crusting with matting of adjacent hairs. A single plaque is usual, but multiple lesions may occur with involvement of entire scalp. Frequently, associated lymphadenopathy is present. Usually caused by zoophilic (M. canis( 犬小孢子菌 ), T. mentagrophytes and T. verrucosum,) or geophilic species. Heals with scarring alopecia. Differential Diagnosis Seborrheic dermatitis, psoriasis, atopic dermatitis, lichen simplex chronicus, alopecia areata. Kerion: Cellulitis, furuncle, carbuncle. Favus: Impetigo, ecthyma, crusted scabies. Laboratory Examinations Wood's Lamp Direct Microscopy Specimens should include hair roots and skin scales. Pluck hairs and use toothbrush to gather specimens. Skin scales contain hyphae and arthrospores. Ectothrix: arthrospores can be seen surrounding the hair shaft in cuticle. Endothrix: spores within hair shaft. Favus: loose chains of arthrospores and airspaces in hair shaft. Fungal Culture With brush-culture technique, a dry toothbrush or brush used for cervical Pap testing is rubbed over area of scale or alopecia; bristles are then inoculated into fungal medium. A wet cotton swab can also be rubbed in affected area, which is then implanted into medium. The cotton-tipped swab from a bacterial culturette, moistened with tap water, can also be used to collect the specimen and sent to a commercial laboratory. Growth of dermatophytes usually seen in 10 to 14 days. Management Prevention Important to examine home and school contacts of affected children for asymptomatic carriers and mild cases of tinea capitis. Ketoconazole or selenium sulfide shampoo may be helpful in eradicating the asymptomatic carrier state. Topical Topical agents are ineffective in management of tinea capitis. Duration of

3 antifungal agents Oral antifungal agents Griseofulvin treatment should be extended until symptoms have resolved and fungal cultures negative. Griseofulvin is considered the drug of choice in the United States. Short-term terbinafine, itraconazole, and fluconazole have been shown to be comparable in efficacy and safety to griseofulvin. Pediatric Dose Micronized: 15 mg/kg per day; maximum 500 mg/d Ultramicronized: 10 mg/kg per day Treatment duration: at least 6 weeks to several months; better absorption with fatty meal. Adult Dose "Gray patch" tinea capitis: 250 mg bid for 1 or 2 months "Black dot" tinea capitis: longer treatment and higher doses continued until KOH and cultures are negative For kerion: 250 mg bid for 4 8 weeks, hot compresses; antibiotics for accompanying staphylococcal infection Terbinafine 250 mg qd. Reduce dosing according to weight in pediatric patients. Itraconazole 100-mg capsules or oral solution (10 mg/ml). Treatment duration: 4 to 8 weeks. Pediatric Dose 5 mg/kg per day Adult Dose 200 mg/d Tinea corporis & Tinea cruris( 体癣 股癣 ) Tinea corporis includes all superficial dermatophyte infections of the skin other than those involving the scalp,hair, palms, soles and nail plate. Tinea cruris is a subacute or chronic dermatophytosis of the groin, pubic regions, and thighs, is a special type of tinea corporis. Causes The most common cause of tinea corporis in the China is T.rubrum, although T. mentagrophytes, T verrucosum Pathophysiology M. canis and are also known to cause infection. Dermatophytes preferentially inhabit the nonliving, cornified layers of the skin, the hair, and the nails, and they generally do not invade below the surface of the epidermis or its appendages. The cell wall of Trichophyton rubrum contains mannan ( 甘露聚糖 ), which may inhibit

4 cell-mediated immunity and proliferation of keratinocytes, and enhances the organism's ability to overcome the skin's natural defenses. The skin response to the superficial infection is increased proliferation, eventually leading to scaling and epidermal thickening. Clinical Manifestation Skin lesion are small to large, scaling, sharply marginated plaques with or without pustules or vesicles, usually at margins. Peripheral enlargement and central clearing produces annular configuration with concentric rings or arcuate lesions; fusion of some lesion can produce gyrate patterns. The lesion typically begins as an annular, erythematous, papulosquamous lesion that may grow rapidly. The lesion may become annular in shape after central resolution occurs. Scaling, crusting, vesicle formation, and papules may also be present. Infections due to zoophilic or geophilic organisms may produce a more intense inflammatory response than those caused by anthropophilic organisms. Diagnosis The diagnosis must be made depending on he clinical features combined with the demonstraion of fungus in skin scrapings. Treatment Topical antifungal agents are effective for treating most cases of tinea corporis and tinea cruris. Oral antifungal agents may be indicated in cases that are extensive, those that involve patients who are immunocompromised, or those that are unresponsive to topical therapy. Topical antifungal agents azoles cream :econazole, ketoconazole, clotrimazole, miconazole, ciclopirox cream terbinafine cream ext,bid,2-4w Oral antifungal agents Itraconazole( 伊曲康唑 )0.2qd 1w or 0.1qd 2w ; terbinafine( 特比萘芬 )0.25/d 1w Tinea Manus et Pedis( 手足癣 ) Tinea pedis is a dermatophytic infection of the feet, characterized by erythema, scaling, maceration, and/or bulla formation. Tinea manus is a chronic dermatophytosis of the hand. Causes Tinea Manus et Pedis are usually caused by T rubrum. Other possible causative organisms include T mentagrophytes and E floccosum. A hot, humid, tropical environment and prolonged use of occlusive footwear, with the resulting complications of hyperhidrosis and maceration, are risk factors for all types of tinea pedis. Certain activities, such as swimming and communal bathing, may also increase the risk of infection. Pathophysiology Dermatophyte fungi invade the superficial keratin of the skin, and the infection remains limited to this layer. Dermatophyte cell walls contain mannans, which can inhibit the body's immune response. T rubrum, in particular, contains mannans that reduce keratinocyte proliferation, and the

5 concomitant decrease in the rate of sloughing results in a chronic state of infection. The cutaneous presentation is dependent upon the host's immune system as well as the infecting dermatophyte. Clinical Manifestation Patients with tinea pedis and manus have 3 possible clinical presentations. Interdigital macerated type The interdigital presentation is the most characteristic type of tinea pedis, with erythema, maceration, fissuring, and scaling, most often between the fourth and fifth toes, and often is accompanied by pruritus. The dorsal surface of the foot is usually clear, but some extension onto the plantar surface of the foot may occur. Chronic hyperkeratotic type The hyperkeratotic type of tinea pedis is characterized by chronic plantar erythema with slight scaling to diffuse hyperkeratosis that can be asymptomatic or pruritic. Both feet are usually affected. Typically, the dorsal surface of the foot is clear, but, in severe cases, the condition may extend onto the sides of the foot. Inflammatory/vesicular type Painful, pruritic vesicles or bullae, most often on the instep or anterior plantar surface, characterize the inflammatory /vesicular type. The lesions can contain either clear or purulent fluid; after they rupture, scaling with erythema persists. Cellulitis, lymphangitis, and adenopathy can complicate this type of tinea pedis. Diagnosis The diagnosis must be made depending on he clinical features combined with the demonstraion of fungus in skin scrapings. Differentials Erythrasma, impetigo, pitted keratolysis, Candida intertrigo, Pseudomonasaeruginosa webspace infection. Psoriasis vulgaris, eczematous dermatitis (dyshidrotic, atopic, allergic contact), pitted keratolysis, various keratodermas Treatment Tinea pedis can be treated with topical or oral antifungals or a combination of both. Topical agents are used for 2-6 weeks. A patient with chronic hyperkeratotic tinea pedis should be instructed to apply medication to the bottoms and sides of his or her feet. For interdigital tinea pedis, even though symptoms may not be present, a patient should apply the topical agent not only to the interdigital areas but also to the soles because of the likelihood of plantar-surface infection. Hyperkeratotic-type tinea pedis is often recalcitrant to topical antifungals alone due to the thickness of the scale on the plantar surface. The concomitant use of topical urea or other keratolytics with topical antifungals should improve the response to topical agents. Whitfield solution, containing benzoic and salicylic acids, can be beneficial. However, patients with extensive chronic hyperkeratotic tinea pedis or inflammatory/vesicular tinea pedis usually require oral therapy, as do patients with onychomycosis, diabetes, peripheral vascular disease, or immunocompromising conditions. Topical imidazoles -- Effective in all forms of tinea pedis but are excellent treatments for interdigital tinea pedis because they are effective against dermatophytes

6 Econazole 1% cream Clotrimazole 1% cream Ketoconazole 1% cream Miconazole2% cream Adult Dose Cream and lotion: Cover affected areas bid for 2-6 wk. Powder: Spray or sprinkle liberally over affected area bid for 2-4 wk. 思考题 : Describe the definition of the superficial mycoses. Describe the clinical type of of tinea capitis and main manifestation respectively. Describe the diagnosis and the differential diagnosis of tinea pedis Learn how to do fungus examine, if you have tinea cruris, to identify the hyphae.