Cutaneous mastocytosis (CM) may be transmitted as an autosomal dominant trait.1 In 1938, Dommartin2 published a thesis on CM in twins in which he reviewed previous cases of monozygotic twins who were concordant for the disease. Then, he described one case in which only one of a pair of dizygotic twins was affected.
In all of the literature we found descriptions of two pairs of dizygotic twins discordant for CM, eight pairs for monozygotic twins both of whom had the disease,3,4 and three pairs of monozygotic twins discordant for the disease.3 Moreover, a set of monozygotic triplets, all of whom were affected with CM, has been described.5 We report a fourth instance of discordance for CM in monozygotic twins and review some possible explanations for this occurrence.
Report of a Case
Four-year-old male twins were seen because of fixed skin lesions, present in one boy,