DISTRIBUTION OF EXTRACELLULAR-MATRIX COMPONENTS IN NUCHAL SKIN FROM FETUSES CARRYING TRISOMY-18 AND TRISOMY-21

We have investigated histologically the elevations of the skin in dors al and lateral neck (nuchal) regions of human fetuses carrying karyoty pes of trisomy 18 (Edwards' syndrome) and trisomy 21 (Down's syndrome) . Cavities filled with interstitial fluid were found in the dermis, ep idermal basement membrane and occasionally in the epidermis of trisomy -18 fetuses, but were not delineated by an epithelium or basement memb rane as judged by the absence of immunostaining for laminin, collagen IV and collagen VII. Dilated vessels were also found al the interface between dermis and subcutis. Neither normal fetal skin nor that of tri somy-21 fetuses contained cavities or dilated vessels. In order to det ect possible alterations of the extracellular matrix in trisomy-18 and trisomy-21 skin, the distribution of glycoproteins, glycosaminoglycan s and proteoglycans was studied immunohistochemically. In trisomy-21 a nd control skin, the dermis stained intensely for fibronectin, whereas the subcutis reacted only weakly. In trisomy-18 skin, the stronger st aining for fibronectin appeared in the subcutis, and the prevailing co llagen type was collagen III, collagen type I being absent. In the ski n of trisomy-21 fetuses, collagen VI was more irregularly arranged and densely packed, whereas collagen I was more widely spaced than in nor mal fetuses. More hyaluronan was present in the dermis and subcutis of trisomy-21 fetuses than in that of trisomy-18 and control fetuses. A correlation seems to exist between undelimited cavities and collagen I II in trisomy-18 skin, and between hyaluronan and the specific arrange ment of collagen in trisomy-21 skin.