Tinea corporis masquerading as subacute cutaneous lupus erythematosus
Published Web Locationhttps://doi.org/10.5070/D34jc2z369
Tinea corporis masquerading as subacute cutaneous lupus erythematosusDepartment of Dermatology, Baylor College of Medicine, Houston, TX. firstname.lastname@example.org
Gunjan M Modi MD, Jennifer L Maender MD, Neil Coleman MD, Sylvia Hsu MD
Dermatology Online Journal 14 (4): 8
Few papers discuss the potential challenge of differentiating dermatophytosis from subacute cutaneous lupus erythematosus. This masquerade, most often manifest on the face, is of both clinical and therapeutic importance. We report a patient whose extensive tinea corporis very closely mimicked SCLE. The threshold for biopsy should be low in cases that exhibit atypical features for either of these entities.
Tinea corporis is a cutaneous mycosis of glabrous skin, most frequently caused by infection with Trichophyton rubrum, Trichophyton tonsurans, Trichophyton mentagrophytes and Microsporum canis . It can be transmitted by direct contact from infected animals or humans, or indirect contact via fomites. Microsporum canis is particularly renowned as a natively zoophilic fungus that may be transferred from domestic pets, specifically cats and dogs. Trichophyton rubrum may cause tinea corporis via auto-inoculation from reservoirs that have colonized the feet.
The classic presentation of tinea corporis is an annular scaly plaque with an erythematous border and central clearing. However, various presentations exist, and previous reports in the literature have documented the close resemblance of certain cutaneous mycoses in both morphology and distribution with cutaneous lupus erythematosus, among other cutaneous diseases.
A 46-year-old white female presented with a two-month history of a diffuse, pruritic skin eruption resistant to treatment with clotrimazole cream prescribed by her primary care physician. The patient asserted that topical clotrimazole treatment had been ineffective despite complete compliance with twice daily application for two weeks. She also noted that the eruption seemed to worsen following exposure to sunlight. She had no prior history of collagen vascular disease and was generally in good health. The patient lived with a roommate who had not experienced any skin abnormalities. She had no other notable past medical, family or social history.
|Figure 1||Figure 2|
|Figures 1-3. Patient at presentation with diffuse, photodistribution of annular, erythematous and scaly patches|
Physical examination revealed numerous well-defined annular erythematous patches and plaques in a symmetrical, photodistributed pattern involving the face, neck, upper chest, back and arms (Figs. 1-3). Her feet were normal and showed no evidence of onychomycosis, plantar scaling, or interdigital maceration. Further examination was unremarkable.
A presumptive diagnosis of subacute cutaneous lupus erythematosus (SCLE) was entertained, and a skin biopsy was taken from the right upper arm for confirmation. Bloodwork was obtained to screen for anti-nuclear antibodies (ANA) and Ro/La autoantibodies. Treatment was withheld pending the results of the histopathology and serum studies.
The skin biopsy specimen showed no evidence of cutaneous lupus. It was then stained for Periodic Acid Schiff (PAS) which was positive, demonstrating branching fungal hyphae in the stratum corneum. (Figure 4) The ANA and Ro/La studies were negative.
The patient returned to clinic and was notified of the biopsy results. Upon further specific questioning, she reported that she recently acquired a new kitten that had patches of fur loss. The patient confirmed that she frequently held the kitten close to her neck and upper chest. Microscopic examination of a skin scraping from the patient with 10 percent potassium hydroxide (KOH) easily revealed innumerable branching hyphae.
Considering the new diagnosis of dermatophytosis (tinea corporis and faciei), the patient was offered but refused systemic antifungal therapy. As an alternative, she was then treated with naftifine cream 1 percent twice daily for 2 weeks, with excellent response (Figure 5 & 6). On follow-up, only mild post-inflammatory pigmentary changes remained.
|Figure 5||Figure 6|
|Figures 5 & 6. Patient at two-week follow-up after using naftifine cream twice daily|
Dermatophyte infections are capable of, and notorious for, demonstrating atypical patterns that can mimic other cutaneous diseases. The differential diagnosis of tinea corporis includes a wide range of skin diseases including lupus erythematosus, psoriasis, erythema annulare centrifugum, pityriasis rosea, nummular eczema, drug eruption, mycosis fungoides, erythema gyratum repens, sarcoidosis, leprosy, and secondary syphilis [1, 2]. Because of the shared characteristic features in these diseases, it is important to consider all possibilities if the KOH exam is normal or if a patient fails to respond to appropriate treatment .
In our case, the clinical morphology and photodistribution of the lesions led us to favor a diagnosis of SCLE. The morphology was so convincing that, combined with the patient's reported failure to improve with topical clotrimazole and reported exacerbation associated with sunlight exposure, a skin biopsy was performed when a simple KOH exam would have revealed the true diagnosis. The history of exposure to a new kitten, if given earlier, would have led to a presumptive diagnosis of dermatophyte infection; however, the photodistribution of the skin lesions is rarely seen in cases of tinea corporis .
Upon review of the literature, the majority of reports describe cases of tinea faciei mimicking chronic cutaneous lupus. There are few papers discussing challenging cases differentiating tinea corporis from SCLE. This masquerade is of great clinical and therapeutic importance. For our patient, a misdiagnosis of SCLE and subsequent treatment with topical steroids or immunosuppressives would have certainly exacerbated the dermatophyte infection. Conversely, with a diagnosis of SCLE, antifungal therapy would be ineffective and would delay appropriate treatment by weeks to months. Because of the striking similarity of morphology in many of the diseases in the differential diagnosis of tinea corporis infection, the threshold for biopsy should be low in cases that exhibit atypical features. It has also been suggested that when non-specific histology is encountered in a biopsy specimen obtained from a patient with an eruption that might be due to fungi, a PAS stain should almost be considered a routine maneuver; this is true even when hyphae are not visible on routine hematoxylin and eosin staining .
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