Pirfenidone-induced photosensitivity confirmed by pathological phototest

Background Idiopathic pulmonary fibrosis (IPF) is an idiopathic interstitial progressive fibrotic lung disease and the most lethal of all interstitial lung diseases. Pirfenidone is a novel antifibrotic and anti-inflammatory agent which reduces decline in lung function and prolonges progression-free survival. It has a favourable benefit-risk profile and is generally well tolerated. However gastrointestinal events, photosensitivity reactions and rash are the most common adverse events. Objective We report a 71-year-old man with 1 week history of erythematous partially pruritic lesions on both sides of the neck and the back of the hands limited to sun exposed areas. He had been diagnosed with IPF and was being treated with pirfenidone (Esbriet) for 8 months. We suspected a photosensitivity reaction caused by pirfenidone. Methods A phototest and a punch biopsy were performed. Results The phototest had a pathological result. The minimal erythema dose was decreased, presenting with erythema and edema starting from 7 mJ/cm2 of UVB and an aberrant response to UVA starting from 2 J/cm2. Histopathological examination revealed spongiotic acute dermatitis with focal presence of necrotic keratinocytes. The patient was diagnosed with pirfenidone-induced photosensitivity and treated with high potency topical steroid leading to the resolution of the lesions, without the need for discontinuation of the drug. Conclusion To our Knowledge, this is the first pirfenidone-induced photosensitivity reported case confirmed by pathological phototest. Patient education and photoprotection advice are essential for prevention.