A Case of Pirfenidone-Induced Photosensitive Drug Eruption

A 75-year-old male was diagnosed with idiopathic pulmonary fibrosis and treated with pirfenidone. He presented with an erythematous thick scaly patch on his face, neck, and both hands and arms. He had a history of significant exposure to sunlight without using sunscreen. All lesions were restricted to sun-exposed areas and appeared one month ago. Histopathological examination revealed necrotic keratinocytes, epidermal spongiosis, liquefaction degeneration of the basal layer, interface dermatitis, solar elastosis, and upper dermal perivascular lympho-histiocytic infiltration. Based on clinical and histopathological findings, the skin lesion could be diagnosed as photosensitive drug eruption induced by pirfenidone. Pirfenidone was discontinued for a month, and the patient was treated with oral and topical corticosteroids. Consequently, the skin lesion almost fully cleared, leaving mild postinflammatory hyperpigmentation. Although there are many reports of photosensitivity reactions to pirfenidone, dermatologists are still not familiar with this drug. Through this case presentation, clinicians should be aware of the potential phototoxic effects of pirfenidone and provide the necessary precautionary information to patients who take pirfenidone.