Simian crease
A simian crease is a single line that runs across the palm of the hand. A
single palmar crease appears in approximately 1 out of 30 people. A single
palmar crease is often a normal finding. However, it may also be associated
with: Down syndrome, Aarskog syndrome, Cohen syndrome, Fetal alcohol syndrome,
Trisomy 13, Rubella syndrome, Turner syndrome, Klinefelter syndrome, Pseudohypoparathyroidism,
Gonadal dysgenesis, and Cri du chat syndrome.