SummaryFolliculitis decalvans (FD) is classified as a primary neutrophilic cicatricial alopecia, and is estimated to account for approximately 10% of all cases of primary cicatricial alopecia. 1 The role of dysfunctional immune activity and the presence of bacteria, particularly Staphylococcus aureus, appear pivotal. We describe a 26-year-old man with a 4-year history of FD that was recalcitrant to numerous systemic and topical therapies, whose disease was virtually cleared during a follow-up of 25 months following a course of treatment with systemic photodynamic therapy (PDT) using ultraviolet light (100-140 J/cm 2 ) with porfimer sodium 1 mg/kg as monotherapy. This is the first report of the use of systemic PDT as a treatment for FD. Systemic PDT has potent antibacterial effects with little or no resistance. In addition, systemic PDT provides local immunomodulation and improved scar healing. Significant adverse effects following systemic PDT with appropriate aftercare are rare. This case demonstrates that systemic PDT is a useful therapy option in the treatment of recalcitrant FD.Folliculitis decalvans (FD) is classified as a primary neutrophilic cicatricial alopecia, which accounts for approximately 10% of all cases of primary cicatricial alopecia.1 Dysfunctional immune activity and the presence of bacteria, particularly Staphylococcus aureus, appear to play pivotal roles. We report a case of FD in a young man who was successfully treated with systemic photodynamic therapy (PDT). ReportA 26-year-old man presented in 2011 with a 4-year history of waxing and waning painful pustulation, hair tufting and scarring, all affecting the vertex of the scalp. He was otherwise healthy. Histological examination of a biopsy taken from the scalp showed evidence of scarring alopecia with superficial follicular and perifollicular abscesses (Fig. 1a). Staining showed Numerous gram-positive bacteria within inflamed hair follicles, and an absence of fungi were evident. Multiple microbacterial swabs from active scalp pustules grew methicillin-sensitive S. aureus. Fungal cultures were negative, as was a screen of connective tissue and skin autoantibodies for bullous pemphigoid and pemphigus.Treatment over the next 3 years involved oral antibiotics (doxycycline, rifampicin and clindamycin), retinoids (isotretinoin and acitretin), prednisolone and ciclosporin. Topical treatments included antibacterial washes, topical antibiotics and topical corticosteroids. Despite these treatments, the disease remained active, with a significant impact on quality of life. The patient was referred for consideration of radiotherapy, a treatment with previously demonstrated effectiveness in FD. 2During the assessment, the patient's youth made it preferable to avoid radiotherapy and instead he was offered a trial of systemic PDT with porfimer sodium (Photofrin, Axcan Pharma Inc, Quebec, Canada) as a novel alternative.