Congenital triangular alopecia may be categorized as a paradominant trait

The genetic basis of congenital triangular alopecia (CTA) is so far not clear. The following arguments are presented in favor of the notion that this may be a paradominant trait. CTA usually occurs sporadically but may exceptionally affect several members of a family. The lesion is usually unilateral but bilateral involvement may likewise occur. CTA has been reported in association with phacomatosis pigmentovascularis, providing evidence that it may originate from loss of heterozygosity. Heterozygous individuals would be phenotypically normal. The trait would be expressed only when postzygotic loss of the corresponding wildtype allele occurred in a early developmental stage. Future molecular research may show whether the concept of paradominant inheritance holds true.