[X-chromosome-linked hereditary dermatoses]

Abstract

In X-linked inheritance, the difference between the terms dominant and recessive is blurred by the Lyon effect. In some X-linked recessive genodermatoses, the Lyon effect makes the detection of heterozygote females possible, either by clinical cromanifestations or by enzymatic demonstration of two functionally different populations of cells. The gene locus of X-linked recessive ichthyosis, however, escapes X-inactivation, but heterozygotes can be detected by enzyme analysis in this condition, too. X-linked dominant gene defects with manifestation in both sexes include keratosis follicularis spinulosa decalvans, and probably also the Bazex syndrome. The group of X-linked dominant gene defects with lethality in the male comprises incontinentia pigmenti, focal dermal hypoplasia, the oral-facial-digital syndrome and the CHILD syndrome. Prenatal diagnosis of severe X-linked conditions can be performed when the underlying defect of cell function is known (Fabry disease, Menkes syndrome). In other severe X-linked disorders, the possibility of prenatal determination of the sex may be considered (Wiskott-Aldrich syndrome, X-linked dominant chondrodysplasia punctata, oral-facial-digital syndrome).