Comment
Tinea manuum is a dermatophytic epidermal infection of the hand. The most common causative organisms are Trichophyton rubrum, T mentagrophytes, and Epidermophyton floccosum. Infection can be acquired from contact with an infected person or animal, fomites, soil, or autoinoculation. Tinea manuum often is associated with tinea pedis. The hand that is used to excoriate the pruritic feet becomes infected, resulting in the classic two feet–one hand syndrome, which this patient did not have.1
Dermatophytes colonize keratin-containing tissues—skin, hair, and nails—utilizing the keratin for nutrients, and they do not invade living tissue in immunocompetent hosts. Dermatophytes cause clinical disease from an allergic host response to fungal antigens or their metabolic products.1 Tinea incognito results from the use of corticosteroids to treat a cutaneous fungal infection. The immunomodulatory effects of corticosteroids alter the appearance of the lesion. Hallmark signs and symptoms of a tinea infection, including scale, prominent border, erythema, and pruritus, can be reduced with corticosteroid use, giving the false impression that the lesion is resolving.2,3
The diagnosis of tinea manuum can be made clinically and often is supported with the findings of a KOH preparation. Scraping from an active scaling border generally provides the best results for obtaining fungal elements. For vesiculobullous lesions, the roof of a vesicle can provide an adequate specimen. Fungal culture and specific dermatophyte testing mediums can be used as confirmatory tests or allow for speciation, which help establish the diagnosis.1
Trichophyton mentagrophytes is a species complex—a group of closely related organisms that share morphologic appearance to the point that boundaries between them often are unclear. It can be identified by gross and microscopic morphology; however, variants of T mentagrophytes (eg, Trichophyton interdigitale, Trichophyton erinacei) require a confirmatory test or molecular analysis to be correctly identified.4-6 The laboratory used at our facility does not routinely attempt to identify the variant due to of lack of clinical significance.7,8
Anthropophilic fungi such as T rubrum, E floccosum, and T interdigitale generally do not cause a robust immunologic reaction. Infection usually is chronic in nature, though cases of pustular and vesicular tinea have been described.9,10Trichophyton erinacei and T mentagrophytes are zoophilic dermatophytes that cause an acute host response and are more likely to present with vesiculobullous lesions. Trichophyton erinacei is the most common fungal pathogen associated with A albiventris and has been isolated from its epidermal mites and quills,11,12 which likely facilitates interspecies transmission and compromises the cutaneous barrier of human hosts when the hedgehog is handled.
Atelerix albiventris is the most common domesticated hedgehog in the United States. These mild-mannered, nocturnal insectivores are unique, low-maintenance pets that have recently gained popularity. They are notable for their propensity to curl into a ball when frightened (Figure 5). The spines are not barbed and do not detach, as those of a porcupine do, but are still capable of piercing the skin. Atelerix albiventris is known to cause zoonotic dermatosis in humans and should be handled with gloves.13 Performing a KOH preparation early in the diagnostic workup can help initiate antifungal therapy, as results of fungal culture can take several weeks.
Figure 5. The patient’s 4-toed, white-bellied African pygmy hedgehog (Atelerix albiventris) in a curled position.
Conclusion
This case illustrates the importance of close follow-up of skin lesions that only partially respond to initial treatment and maintaining a high index of suspicion as exotic pets become popular.