Electron microscopic studies of harlequin fetuses.

Four cases of harlequin fetus of various estimated gestational ages (16, 20, 21, 24 weeks) were examined by light and electron microscopy. When the epidermis was keratinized the following features were commonly found: hyperkeratosis with or without granular cells; dilated hair follicles with plugged keratin; a large number of dense or particle-cored granules in the upper malpighian layer; absence of cementsomes (lamellar bodies); large vacuoles with peripherally located laminations; large mitochondria with vesicular or membranous cristae; and early formation of the marginal band in keratinocytes and abnormal formation of the same in luminal cells of the acrosyringium. A 16-week specimen had no sign of keratinization, which made it difficult to detect these abnormalities; however, it did have large mitochondria in the keratinocytes. The mucous membrane of the lip was thickened but not keratinized.