Urticaria pigmentosa in two pairs of monozygotic twins.

Urticaria pigmentosa occurred in both members of two pairs of twins. Identical blood typings, HLA histocompatibility and appearance strongly indicate that each pair of twins is monozygotic. Except for cutaneous lesions, there were no clinical or roentgenologic evidences of systemic mastocytosis. But latent diabetes mellitus was found in one member. Literature reporting monozygotic twins with urticaria pigmentosa will be discussed in this paper.