77 Fungal Diseases
77 Fungal Diseases | |
|Jenny O Sobera |
|Boni E Elewski |
|Key features |
|Cutaneous fungal infections are broadly divided into those that are limited to the stratum corneum, |
|hair and nails, and those that involve the dermis and subcutaneous tissues |
|Superficial fungal infections of the skin are due primarily to dermatophytes and Candida spp. |
|'Subcutaneous' mycoses are often the result of implantation, while systemic or 'deep' mycoses of the |
|skin usually represent hematogenous spread or extension from underlying structures |
|In the immunocompromised host, opportunistic fungi, e.g. Aspergillus and Mucor, can lead to both |
|cutaneous and systemic infections |
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|This chapter reviews common cutaneous fungal infections, and they are subdivided into three major groups: (1) 'superficial'; (2)|
|'subcutaneous'; and (3) 'deep' or systemic (see Table 77.1). |
|SUPERFICIAL MYCOSES |
|Introduction |
|The superficial mycoses are due to fungi that only invade fully keratinized tissues, i.e. stratum corneum, hair and nails. They |
|can be further subdivided into those that induce minimal, if any, inflammatory response, e.g. pityriasis (tinea) versicolor, and|
|those that do lead to cutaneous inflammation, e.g. dermatophytoses (Table 77.2). The former are discussed first. |
|Non-inflammatory superficial mycoses |
|Synonyms |
|Tinea nigra: tinea nigra palmaris et plantaris, superficial phaeohyphomycosis |
|Piedra: molestia de Beigel, trichomycosis nodularis |
|Pityriasis (tinea) versicolor: tinea versicolor, dermatomycosis furfuracea, tinea flava |
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|Table 77-1. Organization of cutaneous mycoses. |
|ORGANIZATION OF CUTANEOUS MYCOSES |
|Superficial |Invade stratum corneum, hair and nails |
|Subcutaneous |Involve dermis or subcutaneous tissue |
| |Often due to implantation |
|Systemic |Dermal or subcutaneous involvement |
| Deep (true pathogens) |Usually reflects hematogenous spread or extension from underlying structures |
| Opportunistic |Primary or secondary skin lesions in immunocompromised hosts |
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|Table 77-2. Superficial mycoses of the skin. |
|SUPERFICIAL MYCOSES OF THE SKIN |
| |Cutaneous disorder |Pathogen(s) |
|Minimal, if any, inflammation|Pityriasis (tinea) versicolor |Malassezia furfur (Pityrosporum ovale) |
| |Tinea nigra |Exophiala werneckii |
| |Black piedra |Piedraia hortae |
| |White piedra |Trichosporon beigelii |
|Inflammatory response common |Tinea capitis, barbae, faciei, corporis, |Trichophyton, Microsporum, Epidermophyton|
| |cruris, manuum, pedis |spp. |
| |Cutaneous candidiasis |Candida albicans |
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|History |
|In 1846, Eichstedt first noted the disease known today as pityriasis (tinea) versicolor. Over the ensuing 150 years, Malassezia |
|furfur, came to be recognized as the causative organism. Recently, however, studies have pointed to M. globosa as the causative |
|agent1. In 1865, Beigel first described piedra after isolating a fungus from a wig. While the fungus he isolated was likely a |
|contaminant, his clinical description is still valid. Tinea nigra was first described several decades later (1890s) by |
|Cerqueira, who named it 'keratomycosis nigricans palmaris'2. |
|Epidemiology |
|Tinea nigra and piedra typically occur in tropical climates such as Central and South America, Africa, Asia and, occasionally, |
|in the southeastern US. While any race, age or gender may be infected, the typical patient is a young adult. Additionally, |
|Trichosporon beigelii, the cause of white piedra, is also recognized as an opportunistic pathogen. |
|The geographic distribution of Malassezia spp. is worldwide. In fact, it is part of the normal flora of human skin |
|(predominantly M. sympodialis). Although pityriasis (tinea) versicolor occurs most frequently in tropical climates with high |
|ambient temperatures and high humidity, it is also a common disorder in temperate climates. No racial or gender difference has |
|been established. The typical patient is a young adult, but people of any age may develop the disease. Interestingly, Malassezia|
|has an oil requirement for growth, accounting for the increased incidence in adolescents and preference for sebum-rich areas of |
|the skin. Malassezia has been implicated in many other skin diseases, including seborrheic dermatitis and atopic dermatitis, but|
|this remains controversial. Neonatal cephalic pustulosis (neonatal acne) is associated with Malassezia spp. in newborn babies, |
|particularly M. sympodialis, according to a recent study3. |
|Pathogenesis |
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|Exophiala werneckii and Piedraia hortae are both environmental pathogens. E. werneckii (tinea nigra) can be found in soil and |
|sewage and even in shower stalls under humid conditions. The source of exposure to P. hortae (black piedra) is thought to be the|
|soil. There is no known transmission of these organisms from human to human. T. beigelii (white piedra) is also acquired from |
|the environment; however, it may occasionally be part of the normal flora of the skin and mucous membranes4, particularly the |
|groin and axillary skin. |
|M. furfur (and other species) normally lives on human skin in amounts so minute as to be undetectable on KOH examination of |
|stratum corneum5. Pityriasis (tinea) versicolor occurs when the round yeast form transforms to the mycelial form. In tropical |
|climates, this change is a result of high temperatures and high humidity. In temperate climates, various factors have been |
|implicated, including oily skin, excessive sweating, immunodeficiency, poor nutrition, pregnancy and corticosteroid use. Because|
|this yeast is lipophilic, use of bath oils and skin lubricants may increase the risk of disease. Risk factors for pityrosporum |
|folliculitis include chronic antibiotic use, immunosuppression and local occlusion. |
|Clinical features |
|Piedra Piedra is a superficial infection of the hair shaft. 'Piedra' actually translates as 'stone', and fungal elements adhere |
|to one another to form nodules, or 'stones', along the hair shaft. There are two major forms - black piedra and white piedra - |
|and they are distinguished by clinical appearance plus microscopic examination (Table 77.3). Patients with black piedra |
|typically present with asymptomatic brown to black nodules along the hair shaft. Infection usually commences under the cuticle |
|of the hair shaft and extends outward. Hair breakage may occur as a result of shaft rupture at the site of the nodules. As the |
|nodules enlarge they can even envelope the hair shaft (Fig. 77.1). |
|In white piedra, the infection also begins beneath the cuticle and grows through the hair shaft, causing weakening and breaking |
|of the hair. The soft, less adherent nodules of white piedra are generally white but may also be red, green or light brown in |
|color. The incidence of white piedra in the pubic region has increased since the start of the HIV epidemic. In immunosuppressed |
|patients, T. beigelii can cause trichosporosis, a serious systemic infection with fungemia, fever, pulmonary infiltrates, skin |
|lesions (papulovesicular and purpuric, often with central necrosis) and renal disease4. |
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| |Figure 77.1 Causes of nodules on hair shafts. |
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|Table 77-3. Comparison of black and white piedra6. |
|COMPARISON OF BLACK AND WHITE PIEDRA4 |
| |White piedra |Black piedra |
|Nodule color |White (may be red, green or light brown) |Brown to black |
|Nodule firmness |Soft |Hard |
|Nodule adherence to the |Loose |Firm |
|hair shaft | | |
|Typical location |Face and axillae (occasionally in pubic |Scalp and face (occasionally in pubic |
| |region) |region) |
|Climate |Tropical |Temperate |
|Causative organism |Trichosporon beigelii |Piedraia hortae |
|KOH |Non-dematiaceous hyphae with blastoconidia |Dematiaceous hyphae with asci and |
| |and arthroconidia |ascospores* |
|Culture |Moist, creme-colored, yeast-like colonies |Slow-growing, dark brown to black colonies |
|Treatment |Clip affected hairs, wash affected hairs |Clip affected hairs, wash affected hairs |
| |with antifungal shampoo |with antifungal shampoo |
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| |* Sexual reproduction. |
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|Tinea nigra After a 10- to 15-day incubation period, tinea nigra most commonly presents as a single, sharply marginated, brown |
|to gray to green macule or patch that can be velvety or have mild scale. There are usually no associated symptoms (i.e. |
|pruritus), and no predispositions have been identified. While most frequently seen on the palms, tinea nigra can also appear on |
|the soles, neck and trunk. Although palmoplantar lesions are said to resemble acquired acral melanocytic nevi, the former are |
|usually larger, lighter in color and lack the linear striations of the latter. Tinea nigra can also have darker pigmentation of |
|the advancing border as compared to the center. While the disease tends to be chronic, recurrence after effective treatment is |
|infrequent except in the case of re-exposure. |
|Pityriasis (tinea) versicolor Patients usually present with multiple oval to round patches or thin plaques with mild scale. |
|Demonstration of this associated scale may require scratching of its surface. Centrally, within the areas of involvement, the |
|lesions are often confluent and they may be quite extensive. Seborrheic areas, in particular the upper trunk and shoulders, are |
|the favored sites of involvement. Less frequently, lesions are seen on the face (more so in children), scalp, antecubital fossae|
|and groin. When pityriasis (tinea) versicolor involves flexural areas, it is sometimes referred to as 'inverse' pityriasis |
|(tinea) versicolor. |
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| |Figure 77.2 Pityriasis (tinea) versicolor, hyperpigmented variant. Courtesy of Kalman Watsky, M.D. |
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|The most common colors are tan (hypopigmentation; see Chapter 66) and brown (hyperpigmentation; Fig. 77.2); occasionally there |
|is associated inflammation with a pink color. Decreased pigmentation may be secondary to the inhibitory effects of dicarboxylic |
|acids on melanocytes (the latter result from metabolism of surface lipids by the yeast) or decreased tanning, due to the ability|
|of the fungus to filter sunlight. In general, pityriasis (tinea) versicolor is asymptomatic and the major concern is its |
|appearance. |
|Pityrosporum folliculitis This condition is most commonly seen in young women and is characterized by pruritic follicular |
|papules and pustules on the trunk, arms, neck and, occasionally, the face. It is due to excessive growth of P. orbiculare (a |
|culturally identical variant of M. furfur) within the hair follicle with resulting inflammation (from yeast products and free |
|fatty acids produced from fungal lipase). Only yeast forms are observed, i.e. no hyphal forms as in pityriasis (tinea) |
|versicolor. Several Malassezia species have also been implicated in neonatal cephalic pustulosis ('neonatal acne'; Chapter 36). |
|Pathology and fungal culture |
|For both black and white piedra, cut hair shafts are placed in KOH and a 'crush preparation' is examined microscopically. In a |
|black piedra nodule, dematiaceous hyphae are seen around an organized cluster of asci, each of which contains eight ascospores. |
|The ascospores represent the sexual phase of P. hortae. P. hortae grows very slowly when cultured and yields a green to black |
|colony with velvety texture (asexual phase)7. |
|KOH preparation of a crushed white piedra nodule reveals nondematiaceous hyphae, blastoconidia and arthroconidia, representing |
|the asexual state. When cultured, T. beigelii grows rapidly forming moist, cream-colored, yeast-like colonies that some have |
|likened to butter cream frosting. On Mycosel® agar, the organism will be inhibited by the presence of cycloheximide. T. beigelii|
|is often isolated from skin and nail specimens, and the significance of this must be correlated with clinical findings. |
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| |Figure 77.3 Potassium hydroxide preparations. A Superficial skin scrapings from pityriasis (tinea) |
| |versicolor demonstrating yeast and short mycelial forms. B A dermatophyte, in this case T. |
| |tonsurans, demonstrating branching hyphae. A, Courtesy of Ron Rapini, M.D. |
|[pic] |
|Biopsies of pityriasis (tinea) versicolor and tinea nigra are usually not performed as the KOH examination of associated scale |
|is usually diagnostic. In the former, both hyphal and yeast forms are seen; although likened to 'spaghetti and meatballs', the |
|findings more resemble 'ziti and meatballs' (Fig. 77.3A). In the latter, KOH examination reveals septate pigmented hyphae. When |
|biopsy specimens are obtained, similar findings are observed within the stratum corneum. In KOH examination of expressed |
|follicular contents or biopsy specimens of Pityrosporum folliculitis, only yeast forms are seen. Cultures of E. werneckii first |
|appear as pasty, green-black colonies with a yeast-like appearance. However, after about two weeks the appearance changes to |
|that of a fuzzy, dematiaceous (dark in color) mold. Culture of Malassezia is generally not indicated, but if necessary, the |
|plate must be overlaid with sterile oil because of its lipophilic nature. |
|Differential diagnosis |
|Piedra is generally diagnosed by clinical and microscopic inspection of a hair shaft and must be distinguished from pediculosis |
|(nits), hair casts, trichorrhexis nodosa, trichomycosis axillaris (see Chapter 74 and Fig. 77.1) and the scales of psoriasis and|
|eczema. Unlike eczema and psoriasis, the scalp will typically appear normal in piedra. |
|In most patients the diagnosis of tinea nigra is made clinically and confirmed via KOH examination and/or fungal culture. Its |
|distinction from acral melanocytic nevi has been discussed previously (see above); occasionally, tinea nigra could be confused |
|with a fixed drug eruption, post-inflammatory hyperpigmentation, or staining from chemicals, pigments and dyes. Cutaneous |
|melanoma has even been misdiagnosed as tinea nigra, with unfortunate results. |
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|Clinical examination often leads to the correct diagnosis of pityriasis (tinea) versicolor; however, vitiligo, pityriasis alba |
|and other forms of postinflammatory hypopigmentation (see Chapter 66), seborrheic dermatitis, pityriasis rosea and secondary |
|syphilis may mimic the disease. Wood's light examination (revealing bright yellow fluorescence) and then direct microscopy |
|establish the diagnosis. Pityrosporum folliculitis must be differentiated from other causes of folliculitis (see Chapter 40, |
|Table 40.1), in particular itching folliculitis, as well as acne vulgaris. |
|Treatment |
|Clipping hairs with adherent nodules as well as shampooing the affected hairs with 2% ketoconazole[pic] shampoo is usually |
|effective treatment for piedra (Table 77.3). Oral terbinafine is possibly of some therapeutic benefit. For treatment of tinea |
|nigra, topical keratolytic agents such as Whitfield's ointment (typically 6% benzoic acid plus 3% salicylic acid[pic]8) are |
|effective, as are topical antifungal medications, e.g. the azole and allylamine families. Several weeks of therapy may be |
|required to prevent recurrence of disease. Systemic therapy is generally not indicated, and griseofulvin[pic] is not effective. |
|Patients with pityriasis (tinea) versicolor usually respond to topical antimycotic treatments. We instruct the patient to treat |
|all the skin from the neck down to the knees, even if only a small area is clinically involved. Ketoconazole[pic] (1 or 2%) or |
|2.5% selenium sulfide[pic] shampoo is quite effective. Treatment is twice weekly for two to four weeks, the preparation is left |
|on the skin for 10-15 minutes before it is removed. Other topical alternatives include azole/allylamine creams and lotions, 50% |
|propylene glycol in water (cosmetically pleasing), nystatin[pic], salicylic acid[pic] and a variety of over-the-counter dandruff|
|shampoos. Post-inflammatory pigmentary changes may respond to low potency topical corticosteroids but usually require tincture |
|of time. |
|Systemic therapy with ketoconazole[pic], fluconazole[pic] or itraconazole[pic] (see Chapter 128) may provide simple and |
|effective treatment for pityriasis (tinea) versicolor. A regimen of short duration (3 to 7 days) is usually successful. The rate|
|of recurrence of pityriasis (tinea) versicolor is very high, especially in hot humid climates. Patients at high risk for |
|recurrence may be helped by using ketoconazole[pic] shampoo once weekly as 'soap'. Another preventative measure is once monthly |
|dosing of oral ketoconazole[pic], fluconazole[pic] or itraconazole[pic]. Blood monitoring may be required, however, especially |
|in the case of ketoconazole[pic]. |
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