Dermatophyte Infection
It is known that conventional tinea corporis can occur in the setting of CTCL. However, EGR-like eruptions in CTCL can be distinguished from standard tinea corporis by the classic morphology of EGR and clinical history of rapid migration of these characteristic lesions.
Tinea imbricata is known to have a clinical appearance that is similar to EGR, but the infection is caused by Tinea concentricum, which is limited to southwest Polynesia, Melanesia, Southeast Asia, India, and Central America. Although T rubrum was the dermatophyte isolated by Poonawalla et al,3 Jouary et al,5 and in our case, whether T rubrum infection in the setting of CTCL has any impact on prognosis needs further study.
Our case of an EGR-like eruption presented in a patient with SS and tinea corporis. Biopsy specimens showed CTCL and concomitant dermatophytic infection that was confirmed with PAS stain and identified as T rubrum. Interestingly, our patient’s EGR-like eruption cleared with oral terbinafine therapy, consistent with findings described by Poonawalla et al3 and Jouary et al5 in which treatment of the dermatophytic infection led to resolution of the EGR-like eruption, suggesting a causative role.
However, testing for dermatophytes was negative in the other reported cases of EGR-like eruptions in patients with MF, despite screening for the presence of fungal microorganisms using KOH preparation, PAS staining, or fungal culture, or a combination of these methods,3-8 which raises the question: Do the cases reported without dermatophytic infection represent false-negative test results, or can the distinct clinical appearance of EGR indeed be seen in patients with CTCL who lack superimposed dermatophytosis? In 3 prior reported cases of EGR-like eruptions in MF, the eruption was preceded by immunosuppressive therapy.5-7
Further investigation is needed to correlate the role of dermatophytic infection in EGR-like eruptions. Our case and the Jouary et al5 case reported dermatophyte-positive EGR-like eruptions in MF and SS detected with histopathologic analysis and PAS stain. This low-cost screening method should be considered in future cases. If the test result is dermatophyte positive, a 14-day course of oral terbinafine (250 mg/d) might induce resolution of the EGR-like eruption.
Conclusion
The role of dermatophyte-induced EGR or EGR-like eruptions in other settings also warrants further investigation to shed light on this poorly understood yet striking dermatologic condition. Our patient showed both MF and dermatophytes in skin biopsy results, regardless of whether those sites showed erythroderma or EGR-like features clinically. On 3 occasions, antifungal treatment cleared the EGR-like lesions and associated pruritus but not erythroderma. Therefore, it appears that the mere presence of dermatophytes was necessary but not sufficient to produce the EGR-like lesions observed in our case.