Uncommon localization or presentation of tinea infection

Superficial fungal infections are one of the most common dermatoses that may be encountered by the physician. Noyan et al. have reported the case of a 62-year-old diabetic woman who was found to have tinea infection of the scalp and eyebrows caused by Trichophyton violaceum. The diagnosis of tinea infection was missed for some time because she presented with pruritus of the scalp and red, scaly lesions of the eyebrows and scalp, which were initially treated as a steroid-responsive dermatosis. The case highlights the importance of obtaining a good history and examination, and the need to consider a dermatophyte infection when dealing with a dermatosis that may be in an atypical location given the age of the patient, or have an appearance that may be unusual for a fungal infection. Some superficial fungal infections are uncommon in certain age groups. For example, the incidence of tinea capitis is low among adults.1,2 When red, scaly lesions are observed on the scalp a diagnosis of seborrhoeic dermatitis, psoriasis or discoid lupus erythematosus may be more likely. Similarly, onychomycosis and tinea pedis have been uncommonly reported in prepubescent children.3,4 In this age group the differential diagnosis of an abnormal appearing nail includes trachyonychia, 20-nail dystrophy, alopecia areata, lichen planus and trauma.5–7 Tinea pedis may be mistaken for dyshidrotic eczema, shoe dermatitis or juvenile plantar dermatitis.4 Tinea infections caused by dermatophytes of the genera Trichophyton, Microsporum and Epidermophyton, have been named in relation to the anatomical site that is commonly infected, e.g. tinea unguium, tinea pedis, tinea cruris, tinea corporis and tinea capitis, but may cause infection at any anatomical site. Tinea infection has been uncommonly reported, for example, on the penile shaft.8 Most of the cases have been from the Indian subcontinent where males may wear the ‘lengoty’. This is a semiocclusive dress that results in the genitalia being exposed to a warm, occlusive environment, which may facilitate the development of a tinea infection.8 Similarly, tinea mammae (fungal infection of the breast) has been uncommonly described.9 These represent locations where a tinea infection would be uncommon, especially in an immunocompetent individual. The skin usually acts as an effective barrier to deeper penetration of fungal organisms. The barrier function consists of multiple factors, including structural, chemical, non-immunological host defence mechanisms.10 Dermatophytes are not part of the normal human skin flora; however, they are well adapted to infecting skin because they can use skin as a source of nutrients. Complex interaction between the host, fungal organism and iatrogenic factors may result in a presentation that is atypical in localization or clinical features for a fungal infection. In an immunocompromised patient the clinical presentation of tinea infection may be atypical so that the initial diagnosis is not that of a fungal infection. For example, tinea faciale may mimic seborrhoeic dermatitis in a patient with the acquired immunodeficiency syndrome.11 Similarly, a ‘tinea incognito’ clinical picture may be produced following the inappropriate application of a topical corticosteroid to treat a superficial fungal infection. Cutaneous tinea fungal infections are more frequent and severe in individuals who have an immunological defect. This is consistent with the skin having a complex immune system that mediates responses to foreign antigens. When the host is immunocompromised, the infecting organism may be an opportunistic fungal organism or a dermatophyte that would generally not be expected to be recovered from that site. With the increase in the number of patients who are immunocompromised due to a variety of causes, there has been a change in the spectrum of infection caused by the classic fungal pathogen. The diabetic patient reported by Nolan et al. may fall into this category. Deep or disseminated dermatophyte fungal infections are generally rare and are more likely to occur in immunocompromised individuals.12 From the management viewpoint, when a chronic inflammatory dermatosis is poorly or non-responsive to standard therapy, or when the clinical presentation of a dermatosis is atypical, it is important to re-evaluate the patient with history and examination conducted to exclude a possible fungal infection. Simple laboratory procedures may be of help in arriving at the correct diagnosis.13 Skin scrapings, and if appropriate, a nail specimen, can be processed for light microscopic examination. If possible, a fungal culture should be planted as this may help identify the causative organism and enable the physician to carry out the most appropriate management. Similarly, a biopsy may aid in the diagnosis; however, it may not be possible to identify the fungal organism definitively using this test

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