Recalcitrant dermatophytosis: clinicomycological features and challenges in management

Dermatophytosis is the most common fungal infection encountered by primary care providers and outpatient physicians. In recent years, new patient populations with chronic infections - accompanied by a history of recurrences and relapses - presenting with unusual or severe manifestations have been reported worldwide. This is broadly referred to as recalcitrant dermatophytosis.

Through an electronic literature search spanning the last 25 years, we discuss systemic treatment options for recalcitrant dermatophytosis, including conventional terbinafine and itraconazole treatments, either alone or in combination with topicals. Dosing strategies and treatment durations are summarized along with potential reasons for treatment failure. There is mounting evidence suggesting that dermatophyte resistance is a significant cause of terbinafine nonresponse, making itraconazole the preferred first-line treatment. However, pharmacokinetic variability may cause sub-therapeutic exposure and induce resistance to itraconazole. In some instances, super-bioavailable itraconazole may be a consideration. Corticosteroids should be strictly avoided.

The current literature is limited by case reports and small case series. Newer triazoles and ketoconazole have been reported as drugs of last resort. Increased advocacy and collaboration are needed to standardize the management of recalcitrant dermatophytosis including antifungal susceptibility testing, especially concerning special populations such as pregnant individuals and children.