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1 Go Back to the Top To Order, Visit the Purchasing Page for Details Chapter Fungal Diseases Fungi are eukaryotic microorganisms that have a cellular wall and do not photosynthesize. They parasitize organisms or exist as spores. In superficial mycoses, fungi invade keratinized tissue such as the horny cell layer, hair and nails. In deep fungal infection, fungi tend to parasitize the dermis and deeper layers. A. Dermatophytoses Table.1 Classification of dermatophytes. Trichophyton T. rubrum T. mentagrophytes T. verrucosum T. violaceum T. schoenleinii T. tonsurans T. concentricum T. equinum Microsporum M. canis M. gypseum M. audouinii M. cookei M. equinum M. ferrugineum M. gallinae M. nanum Epidermophyton E. floccosum Table.2 Classification of tinea. Tinea superficialis Tinea pedis Tinea unguium Tinea manus Tinea cruris Tinea corpooris Tinea faciei Tinea capitis Tinea incognito Tinea profunda Kerion celsi Sycosis trichophyica Granuloma trichophyticum Trichophytid Outline They are caused by dermatophytes that parasitize the skin, the horny cell layer in particular. They have various common names, depending on the affected site. The main subtypes are tinea pedis (commonly called athlete s foot; it accounts for more than half of tinea cases), tinea capitis (scald head, which occurs frequently in childhood), tinea corporis (serpigo, which heals in the center to present a ring shape or lesion) and tinea cruris (jock itch, which involves the genitalia). The causative dermatophyte is microscopically identified from scales of the lesion or nail using KOH solution. The treatments are topical or oral antifungal agents. Classification Fungi called dermatophytes parasitize the horny cell layer, causing dermatophytosis. Dermatophytes are divided into three genera, each with various species (Table.1). The most common dermatophytes are Trichophyton rubrum and Trichophyton mentagrophytes. Because dermatophytes feed on keratin, they usually infect the epidermal horny cell layer, nails and hair follicles, causing lesions (tinea superficialis). Dermatophytosis in which dermatophytes proliferate in the dermis and deep dermal layers is called tinea profunda (Table.2). The name of the dermatophytosis differs by the location. Laboratory findings, Diagnosis Diagnosis of dermatophytosis is confirmed when dermatophytes or segmental spores of 3 mm to 4 mm in diameter containing septum are found microscopically with KOH solution in a specimen taken from a scale, blister covering, nail or hair (Figs..1 and.2). For observation by light microscopy, a specimen is placed on a slide glass with 1 or 2 drops of 20% KOH solution and then covered with glass and heated for a few minutes. Use of DMSO-added KOH solution makes rapid microscopic examination 468

2 A. Dermatophytoses 469 possible, because heating is unnecessary. Microscopy with KOH solution is always used when dermatophytosis is suspected. Other major tests are culture in Sabouraud s glucose agar for color tone and morphological observation of the colony, morphological observation of conidium by slide culture, molecular examination by PCR or in situ hybridization, and regular hematoxilin-eosin stain. Treatment The basic treatment for all sites infected with tinea superficialis except hairy areas is topical application of antifungal agents such as imidazole. For tinea superficialis in hairy areas, intractable tinea, and tinea profunda with cutaneous and subcutaneous symptoms (e.g., hyperkeratotic tinea pedis, tinea unguium, kerion celsi and granuloma trichophyticum), useful treatments are systemic itraconazole and terbinafine hydrochloride. Griseofulvin is no longer commonly used in Japan. Fig..1 Trichophyton rubrum. Filamentous hyphae (arrows) are microscopically observed in the horny cell layer with the addition of KOH solution. a. Superficial dermatophytic infections 1. Tinea pedis It is commonly called athlete s foot. More than half of tinea cases are tinea pedis. Multiple dermatophytes are seen in the scales. The most common causative fungus is Trichophyton rubrum, followed in frequency by Trichophyton mentagrophytes. Tinea pedis is classified by clinical features into three clinical subtypes. Interdigital erosive: This is the most common of the three subtypes. The fourth toe cleft is most commonly affected. It begins with erythema and vesicles on the interdigital region, leading to scaling. The skin lesion is often infiltrative, softening to become whitish, then exfoliating and becoming erosive (Fig..3). Itching is intense. Secondary infection from erosion causes sharp pain or cellulitis. Vesicular scaling: The plantar arch and the base of the toes are most frequently involved. Multiple vesicles occur and dry, leading to scaling. It tends to appear during the rainy season and subside in autumn. Hyperkeratotic: It occurs most frequently on the heels. Hyperkeratosis causes roughness of the skin. Itching is rarely present, but sharp pain results from cracking. This type is resistant to topical agents; oral antifungals are effective. 2. Tinea unguium Synonym: Onychomycosis (referring to nondermatophytic and dermatophytic infections of nail plate) Fig..2 Histopathology of tinea. Filamentous hyphae (arrows) are observed in the horny cell layer. Tinea unguium frequently occurs on the first toe, often secondarily after tinea pedis. Usually, white nail (leukonychia) first Fig..3 Tinea pedis. bottom: Tinea pedis with secondary infection.

3 470 Fungal Diseases Fungi and molds MEMO Molds and mushrooms are fungi. Yeasts, which are used for food products and are mononucleated, are also regarded as fungi. A fungus is composed of a long, thin hypha and a spore that is usually spherical and proliferates by germination. Spores parasitize humans by becoming airborne and attaching to the body, where they form hyphae and reproduce sexually or asexually. Spores may be elongated, depending on the environment, resembling hyphae (pseudohyphae). In culture media such as slide culture, hyphae with a characteristic shape (conidiophores) and asexual spores called conidia form. The conidium consists of the macroconidium and the microconidium. Disease-causing fungi may be identified by the features of the hyphae. appears at the tip of the toenail and gradually spreads to the nail matrix. The nail becomes fragile and pulverizes when cut with clippers (Fig..4). The fungal elements occur mostly in the deeper portions of the nail plate and in the hyperkeratotic nail bed, rather than on the surface of the nail plate. It is often left untreated for a long period because of its asymptomatic nature. Dermatophytes spread in a patient from a tinea unguium skin lesion to a tinea pedis skin lesion, causing autoinfection and intrafamilial infection. It is sometimes difficult to improve with topical agents. Oral antifungal drugs are more effective. 3. Tinea manus Fig..4 Tinea unguium. The skin lesion may be hyperkeratotic, vesicular or scaling. One hand, rather than both, tends to be involved (Fig..5). The majority of patients have tinea pedis as a complication. Topical antifungal agents are the main treatment. 4. Tinea cruris It is commonly called jock itch. The crotch and buttocks of adult men are most frequently affected; the scrotum is rarely involved. The same type of skin lesion as in tinea corporis appears, often symmetrically. Itching is intense. The treatments are topical and oral antifungal agents. Fig..5 Tinea manus. The interdigital areas, fingers and fingernails are frequently affected. 5. Tinea corporis Commonly known as serpigo, it appears as small erythematous papules on the trunk and extremities, gradually spreading centrifugally. The papule tends to heal centrally, giving the lesion a ring shape (Fig..6). Although the center of the lesion subsides with mildly abnormal pigmentation, the periphery is elevated, and papules, vesicles and scales form there. Itching is present. As in tinea pedis, the causative dermatophyte in most cases of tinea corporis is Trichophyton rubrum. Tinea corporis is occasionally caused by Microsporum canis, which parasitizes dogs and cats. Tinea corporis caused by Microsporum canis is characterized by

4 A. Dermatophytoses 471 Clinical images are available in hardcopy only. Clinical images are available in hardcopy only. Clinical images are available in hardcopy only. Fig..6 Tinea corporis. Erythematous lesions enlarge centrifugally. The center tends to heal and the rim elevates in a banked shape. intense inflammatory symptoms. Topical and oral antifungal agents are the main treatments. 6. Tinea faciei It is a Trichophyton infection on the face. Unlike in eczema, the plaques have a slightly elevated rim and tend to heal centrally (Fig..7). 7. Tinea capitis Commonly known as scald head, this occurs most frequently in children. Trichophyton infection in hair follicles results in sharply edged alopecia of the scalp. There are dry pityroid scales and short, broken off hairs in the lesion. Subjective symptoms such as pain are not present. Head hair is sparse. Inflammation is absent. Tinea capitis accompanied by itching and black dot formation at the follicles after the hairs break off is called black dot ringworm; it is associated with misuse of topical steroid ointments, and its incidence has been increasing (Fig..8). Oral antifungal drugs are the first-line treatment. The affected site should be kept clean and dry. Fig..7 Tinea faciei. 8. Tinea incognito The tinea lesion heals centrally; however, if tinea is misdiagnosed as eczema and topical steroids are misused for treatment, Fig..8 Tinea capitis.

5 472 Fungal Diseases the inflammation subsides and the characteristic central healing in the lesion is not distinctly observed. This complicates diagnosis, and such manifestation is called tinea incognito. Tinea incognito presents clinically atypical cutaneous symptoms in such a case (Fig..9). b. Deep dermatophytic infection Instead of remaining in their usual location of the epidermal horny cell layer or nail plate, fungi of the genus Trichophyton invade the dermis or subcutaneous tissue, causing skin lesions. Fig..9 Tinea incognito causes different clinical symptoms from typical tinea. Fig..10 Kerion (celsi). Fig..11 Sycosis trichophytica. 1. Kerion (celsi) Kerion is most common on the scalp but can be produced in other sites. Pityriatic scales appear in the scalp, as in tinea capitis. Inflammation soon occurs, leading to erythema, follicular papules, pustules, and flat or dome-shaped abscesses (Fig..10). The lesions are accompanied by sharp pain, mild pulsation and discharge of pus. The hairs in the lesion fall out. There are systemic symptoms such as swelling of the regional lymph node and fever. Most cases are caused by misuse of steroid ointments on tinea capitis of the scalp, and the incidence has been increasing in recent years. The most common causative agent of kerion celsi is Microsporum canis, which infects humans through their pets. Infants are most frequently affected. Histopathologically, Trichophyton infection is found in hairs; inflammatory cellular infiltration occurs in peripheral follicles. However, Trichophyton does not proliferate in the dermis. The main treatment is oral antifungal agents. The incidence of Trichophyton tonsurans has been increasing in recent years (MEMO). 2. Tinea barbae This is equivalent to kerion celsi at sites with barbae (mustache, beard). The upper lip and its periphery are most frequently involved (Fig..11). Reddening and swelling occur in the entire area with barbae. Pus is discharged from the hair follicles. The hairs come out easily when pulled. Most cases are caused by shaving or misuse of steroids. The treatments are the same as for kerion celsi. Trichophyton tonsurans MEMO Group infection of Trichophyton tonsurans occasionally occurs in Japan. The main skin lesions caused by this fungus are kerion celsi, black-dot ringworm, and tinea corporis. There are cases in which annular erythema, characteristic of tinea, is only vaguely seen. Athletes of sports with much physical contact, such as wrestling and judo, are most frequently affected; all team members should receive a medical checkup. Oral antifungal drugs are the first-line treatment, followed by the same treatments as for tinea.

6 B. Candidiases Trichophytic granuloma Synonym: Majocchi s granuloma A nodule appears intradermally, subcutaneously, or in a skin lesion caused by tinea superficialis. Flat infiltrative plaques or tumorous plaques may form (Fig..12). The granuloma may occur locally (localized granuloma trichophyticum) or multiply on the whole body (generalized ganuloma trichophyticum). Localized ganuloma trichophyticum may be associated with misuse or abuse of topical steroids. Oral antifungal drugs are the main treatment. The condition often occurs in immunocompromised individuals such as organ transplantation recipient. Fig..12 Granuloma trichophyticum. Infiltrative skin lesion from prolonged use of topical steroids on granuloma trichophyticum. This was misdiagnosed as eczema. Trichophytid MEMO Trichophytid is thought to be an allergic reaction to fungal components or metabolites. Like tuberculid, this is an id lesion, which reflects the intense inflammatory reaction that accompanies tinea infection. Patients with severe tinea are most frequently affected. Erythema, papules and vesicles occur on contralateral sites of the body that are not affected by tinea. Trichophytid often occurs during the exacerbation of kerion celsi or tinea pedis. Fungi of the genus Trichophyton do not exist at sites of eruptions. B. Candidiases Outline It is an infection of the skin or mucous membrane caused by yeasts of the genus Candida. It is classified by location and clinical features into three subtypes: cutaneous candidiasis (e.g., candida intertrigo, erythema mycoticum infantile, candidal paronychia), mucosal candidiasis (thrush, genital candidiasis), and atypical candidiasis (e.g., chronic mucocutaneous candidiasis). It may also occur as an occupational disease in workers whose hands are in frequent contact with water, or as a sexually transmitted disease or an opportunistic infection resulting from immunodeficiency. The affected site should be kept clean and dry. The antifungal imidazole is topically applied. Classification, Pathogenesis, Clinical features There are seven to ten virulent species in the genus Candida (Table.3). The main causative species is known to be Candi- Table.3 The Candida species most frequently cultured from humans. C. albicans C. tropicalis C. guilliermondii C. krusei C. kefyr C. glabrata C. parapsilosis C. lusitaniae C. zeylanoides C. glabrata Go Back to the Top To Order, Visit the Purchasing Page for Details