Contact Dermatitis Masquerading as Folliculitis Decalvans: Methylisothiazolinone Strikes Again!

摘要

Methylisothiazolinone (MI) is currently a leading cause of contact dermatitis, and can present with unusual clinical manifestations. An atopic male patient in his 40s had been experiencing an itchy and burning dermatosis on his scalp for nearly 1 year presenting follicular pustules and crusts, tufted hairs, and subtle areas of cicatrization (Fig. 1A). Bacterial swabs had repeatedly shown the growth of Staphylococcus yaureus, and because of a clinical suspicion of folliculitis decalvans, he had received treatments with topical corticosteroids and oral antibiotics, all with only partial and temporary relief. Upon referral, clinical examination showed weeping erythematosquamous lesions with a sharp demarcation on the scalp along with infiltrated red lesions unevenly distributed over the face (Fig. 1B). Interestingly, the dermatosis would burst out in flares, thereby occasionally extending to both arms and, sometimes, even producing a burning sensation of his mouth and nose mucosa. A skin biopsy taken from the scalp, to differentiate between folliculitis decalvans and a superinfected (contact) dermatitis, was in favor of the latter demonstrating, however, a normal epidermis and a remarkable dermal lymphocytic infiltrate accompanied by eosinophils.