Trichophyton rubrum-Syndrom und Tinea incognita unter immunsuppressiver Behandlung mit Leflunomid und Fumarsäureestern bei Patienten mit rheumatoider Arthritis und Psoriasis vulgaris

[Recurrent tinea corporis generalisata due to Terbinafine-resistant Trichophyton rubrum strain : Long-term treatment with super bioavailability itraconazole]

For more than 30 years, an 82-year-old man has been suffering from tinea corporis generalisata in the sense of Trichophyton rubrum syndrome. The patient received long-term treatment with terbinafine. Fluconazole had no effect. There was an increase in liver enzymes with itraconazole. Super bioavailability (SUBA) itraconazole was initially not tolerated. A therapy attempt with voriconazole was successful, but was stopped due to side effects. The Trichophyton (T.) rubrum strain isolated from skin scales was tested for terbinafine resistance using the breakpoint method and found to be (still) sensitive. Sequencing of the squalene epoxidase (SQLE) gene revealed a previously unknown point mutation of the codon for isoleucine ATC→ACC with amino acid substitution I479T (isoleucine479 threonine). Long-term therapy with terbinafine 250 mg had been given every 3 days since 2018. In addition, bifonazole cream, ciclopirox solution, and occasionally terbinafine cream were used. The skin condition was stable until an exacerbation of the dermatophytosis in 2021. There were erythematosquamous, partly atrophic, centrifugal, scaly, confluent plaques on the integument and the extremities. Fingernails and toenails had white to yellow-brown discoloration, and were hyperkeratotic and totally dystrophic. T. rubrum was cultured from skin scales from the integument, from the feet, from nail shavings from the fingernails and also toenails and detected by PCR. In the breakpoint test, the T. rubrum isolates from tinea corporis and nail samples showed a minimum inhibitory concentration (MIC) of 0.5 µg ml-1 (terbinafine resistance in vitro). Sequencing of the SQLE gene of the T. rubrum isolate revealed evidence of a further point mutation that led to amino acid substitution I479V (isoleucine 479 valine). Long-term therapy was started with SUBA itraconazole: 14 days 2 × 1 capsule daily, then twice weekly administration of 2 × 50 mg. During breaks in therapy, the mycosis regularly flared up again. Finally, 50 mg SUBA itraconazole was given 5 days a week, which completely suppressed the dermatophytosis. Topically, ciclopirox and miconazole cream were used alternately. In conclusion, in the case of recurrent and therapy-refractory dermatophytoses caused by T. rubrum, terbinafine resistance must also be considered in individual cases. An in vitro resistance test and point mutation analysis of the squalene epoxidase gene confirms the diagnosis. Itraconazole, also in the form of SUBA itraconazole, is the drug of choice for the oral antifungal treatment of these patients.

[Terbinafine-resistant dermatophytoses and onychomycosis due to Trichophyton rubrum]

BACKGROUND

In recent years, therapy-refractory courses of dermatophytoses have increasingly become the focus of attention. The most frequent pathogens are Trichophyton (T.) rubrum and T. mentagrophytes. In addition to local therapy, first-line treatment includes terbinafine, an allylamine antifungal agent that acts by inhibiting squalene epoxidase and thus interfering with ergosterol synthesis. In refractory cases, terbinafine resistance due to point mutation in the squalene epoxidase gene has been frequently detected.

OBJECTIVES

The aim is to present specific aspects in the epidemiology of dermatophytoses with terbinafine resistance and to illustrate them on the basis of four patient cases including diagnostic procedures.

MATERIALS AND METHODS

A review of handbook knowledge, a selective literature search, and a review of four patient cases were performed.

RESULTS

Detection of the terbinafine resistance was performed by in vitro testing using the breakpoint method as well as sequencing of the Trichophyton isolate and detection of the point mutation with amino acid substitution at position L393F or F397L of squalene epoxidase.

CONCLUSION

In refractory and recurrent dermatophytoses, terbinafine resistance should be considered, especially in T. mentagrophytes and T. rubrum, and in vitro resistance testing of the dermatophyte and point mutation analysis of squalene epoxidase (SQLE) should be performed. Therapeutically, intermittent administration of itraconazole in combination with antifungal local therapy is recommended. Nevertheless, a recurrent course is to be expected and long-term therapy with itraconazole is usually necessary.