Extensive Pustular Tinea Incognita During Late Pregnancy: A Case Report.

Tinea incognita is an atypical presentation of dermatophytosis, usually modified by prior corticosteroid exposure, which may obscure the clinical diagnosis and mimic inflammatory dermatoses. We report the case of a 27-year-old woman at 35 weeks of gestation who presented with a three-week history of painful inflammatory lesions involving the gluteal region and posterior thighs. The eruption initially presented as bilateral erythema of the inguinal folds and gluteal area and worsened rapidly after topical mometasone treatment. Physical examination revealed extensive, symmetrical, well-demarcated erythematous plaques with fine scaling and numerous peripheral pustules. Given the pustular morphology and pregnancy context, pustular psoriasis was initially considered. However, direct mycological examination was positive, and fungal culture subsequently identified Trichophyton rubrum, confirming the diagnosis of pustular tinea incognita. Treatment with oral itraconazole led to marked clinical improvement. This case highlights the importance of considering dermatophytosis in the differential diagnosis of pustular eruptions during pregnancy, particularly when lesions worsen after topical corticosteroid use. Early mycological testing can prevent diagnostic delay and inappropriate escalation of anti-inflammatory or immunosuppressive therapy.