Monozygotic twin discordance for phacomatosis cesioflammea further supports the post-zygotic mutation hypothesis.

Phacomatosis pigmentovascularis (PPV) is a group of sporadic skin disorders combining widespread cutaneous capillary malformations and pigmented nevi. Etiopathogenesis of the various forms of PPV is unknown, although a non-allelic twin spotting has been proposed as the most likely underlying mechanism. We report on the second instance of monozygotic twin discordance for PPV.