A crease on the palm of the hand, so termed because of its similarity to the transverse flexion crease found in some monkeys. Normally the palm of the hand at birth contains several flexion creases, two of which are separate and approx, transverse. When these two appear to fuse and thus form a single transverse crease, a simian crease is present. The crease may be present in a variety of developmental abnormalities; including Down syndrome, rubella syndrome, Turner’s syndrome, Klinefelter’s syndrome, pseudohypoparathyroidism, and gonadal dysgenesis.
A solitary and prominent horizontal line on the palm of the hand. This characteristic is linked to chromosomal abnormalities like Down’s syndrome.