Paradominant inheritance may explain familial occurrence of cutis marmorata telangiectatica congenital

Cutis marmorata telangiectatica congenita (CMTC) is a rare congenital vascu lar anomaly that virtually always occurs sporadically and in a patchy, quad rant, unilateral or otherwise segmental manifestation. This would suggest m osaicism of a postzygotic mutation. Some authors, however, described CMTC o ccurring in several members of a family. This paradox may be explained by t he concept of paradominant inheritance. Heterozygous individuals carrying a 'paradominant' mutation are, as a rule, phenotypically normal. The mutatio n can therefore be transmitted unperceived through many generations. The tr ait only becomes manifest when a postzygotic mutation occurring during earl y embryogenesis gives rise to loss of heterozygosity and forms a mosaic pop ulation of cells being either homozygous or hemizygous for the mutation. Th is concept may explain the occasional familial occurrence of CMTC. Copyrigh t (C) 2001 S. Karger AG, Basel.