[Normal development of human fetal skin].

Over the past few years, the use of fetal skin biopsies for prenatal diagnosis of severe inherited skin diseases has illustrated the practical importance of the structural and antigenic knowledge of normal human fetal skin. During the first 10 weeks of gestation the basic structure and antigenicity of epidermis is built up and at about 18 weeks gestation, the period in which fetal skin biopsy is usually carried out, most of the structural and antigenic markers are fully formed and usable for prenatal diagnosis: the dermal-epidermal junction is complete with hemidesmosomes and anchoring fibrils; type IV collagen and laminin are already demonstrable and useful for dermal epidermal junction mapping; other monoclonal or polyclonal markers such as GB3 or LH 7:2 are already present. At this time pilosebaceous units are present and keratinization is well developed in follicular epidermis; interfollicular keratinization, in contrast, does not begin before 24 weeks of gestational age. The appearance of sweat glands on general body surface occurs only after 24-27 weeks gestation.