FS04.7 Atypic T‐cell infiltrate by isothiazolinone. Question to discuss

Methyl(chloro)isothiazolinone is an effective preservative and a major cause of cosmetic allergy in most European countries. On the face unusual clinical presentations are seborrhoeic dermatitis, lupus erythematosus, lymphocytic infiltrate, photodermatosis or atopic dermatitis. Three patients who suffered a chronic, recurrent, itchy and generalized cutaneous erytematous-desquamative and eczematous eruption with a common pathologic event, an atypical lymphoid infiltrate, whose induction by a contact allergen can be discussed are presented. The first, a 59 years old man showed a biopsy with an atypical dermal-epidermal T cell infiltrate of mycosis fungoides and monoclonal TCR-rearrangement. The second, a 74 years old man showed an atypical lymphoid infiltration with polyclonal TCR-rearrangement and a second biopsy showed an eczematous pattern. The third, a 50 year old man with pathology of plaque parapsoriasis with atypical lymphoid infiltrate. The three patients showed strong positive reaction to methyl(chloro)isothiazolinone (0.01%aq.) Trolab,,μ. Avoiding the allergen the cutaneous eruption disappeared and any recurrence has been observed yet. Pathologic criteria for mycosis fungoides remains controversial and could not be done only on the basis of cellular density or the percentage of atypical T-cells. Autoinvolutive mycosis fungoides shows the unknowledge of its pathogenesis. How some allergens could affect on the cellular life needs further studies. We highly recommend to patch test all patients with atypical cutaneous T-cell infiltrates.