CHARACTERISTIC MORPHOLOGIC ABNORMALITY OF HARLEQUIN ICHTHYOSIS DETECTED IN AMNIOTIC-FLUID CELLS

We have examined cells from amniotic fluid obtained at 17 and 21 weeks ' gestation and fetal skin biopsy samples from a fetus at risk of harl equin ichthyosis by light and electron microscopy. Clumps of abnormall y keratinized cells that had a large number of lipid droplets in the c ytoplasm were seen within both the 17- and 21-week amniotic fluid cell pellets. The cells in these clumps were similar to the thick layers o f keratinized cells observed in the skin biopsy and autopsy samples. M orphologic examination of the fetal skin biopsy samples obtained at 21 weeks gestation revealed the characteristic changes of harlequin icht hyosis. The intraepidermal portions of hair canals had an excessive nu mber of layers of keratinized cells. Normal lamellar granules were abs ent but abundant membrane-bound vesicles of a similar size and a numbe r of dense bodies were observed in the cells of the upper intermediate layers of the epidermis. Autopsy skin samples of the terminated fetus at the twenty-third week of gestation showed structural changes that corresponded to those of the amniotic fluid cells and the fetal skin b iopsy samples, although the periderm was gone in all the regions. Our findings of amniotic fluid indicate that the characteristic epidermal abnormality of harlequin ichthyosis has been expressed at 17 weeks ges tation in some parts of the body or structures of fetal skin (e.g., ha ir canals) that keratinize before interfollicular epidermis. Moreover, the results suggest that harlequin ichthyosis can be detected in uter o by morphologic analysis of amniotic fluid cells obtained by amniocen tesis.