Paradominant inheritance may explain familial occurrence of Cutis marmorata telangiectatica congenita.

Cutis marmorata telangiectatica congenita (CMTC) is a rare congenital vascular anomaly that virtually always occurs sporadically and in a patchy, quadrant, unilateral or otherwise segmental manifestation. This would suggest mosaicism of a postzygotic mutation. Some authors, however, described CMTC occurring in several members of a family. This paradox may be explained by the concept of paradominant inheritance. Heterozygous individuals carrying a 'paradominant' mutation are, as a rule, phenotypically normal. The mutation can therefore be transmitted unperceived through many generations. The trait only becomes manifest when a postzygotic mutation occurring during early embryogenesis gives rise to loss of heterozygosity and forms a mosaic population of cells being either homozygous or hemizygous for the mutation. This concept may explain the occasional familial occurrence of CMTC.