Successful use of photodynamic therapy for refractory cutaneous Langerhans cell histiocytosis: A case report

Cutaneous manifestations of Langerhans cell histiocytosis (LCH) are diverse and may mimic various dermatologic conditions, often leading to diagnostic challenges. We report a case of a 44-year-old woman who presented with multiple erythematous papules on the scalp, associated with tenderness and pruritus persisting for several months. Histopathological examination and immunohistochemical staining confirmed cutaneous LCH, consistent with her known systemic LCH involving the pituitary gland and sternum. An initial systemic chemotherapy protocol comprising weekly vinblastine and prednisolone, followed by an eight-week consolidation phase, failed to elicit a therapeutic response. Subsequent treatment with low-dose cytarabine (100 mg/m²), administered as a 5-day course every 28 days, also failed to achieve disease control. Local scalp radiotherapy yielded partial improvement but was limited by adverse effects. Due to chemoresistance and intolerance to radiotherapy, 5-aminolevulinic acid (5-ALA) based photodynamic therapy (PDT) was initiated. PDT led to marked clinical improvement of cutaneous lesions with minimal adverse effects. However, disease recurrence necessitated additional PDT sessions, which remained effective upon relapse. This case highlights the potential role of PDT as a safe and effective alternative for managing cutaneous LCH refractory to conventional therapies.