Transient leucoderma appearing in an untreated area following contact immunotherapy for alopecia areata

One of the possible unwanted side effects following contact immunotherapy of alopecia areata is skin hypopigmentation, either in the form of a transient, post-inflammatory hypopigmentation or as the development of a persistent, depigmented patch. A case of leucoderma occurring on the forehead of a 16-year-old girl following application of squaric acid dibutylester to the scalp for the treatment of alopecia areata is described. Past medical and family history were negative for vitiligo and autoimmune disorders. The hypopigmented patch was distant from the scalp area where squaric acid dibutylester had been applied, and it was not preceded by any sign of eczema, erythema or itch in the same area. Moreover, it faded as soon as treatment was discontinued. A 4-year follow-up revealed no evidence of vitiligo. In conclusion, the possible occurrence of a transient leucoderma in untreated areas should be included among the side effects of contact immunotherapy of alopecia areata with squaric acid dibutylester.