Definition of Simian crease:

A simian crease is a single line that runs across the palm of the hand. People normally have three creases in their palms.

The term "simian crease" is not used much anymore since it tends to have a negative meaning (it refers to monkey or ape). The crease is usually just refered to as a single palmar crease.

Considerations:

Strong lines (called palmar flexion creases) appear on the palms of the hands and soles of the feet. The palm normally has three of these creases. But sometimes, the horizontal creases join together to form a single one.

Palmar creases develop while the baby is growing in the womb, usually by the 12th week of gestation.

A single palmar crease appears in approximately 1 out of 30 people. Males are twice as likely as females to have this condition. Some palmar creases indicate problems with development and are associated with disorders like Down syndrome.

Common Causes:

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
• Cri du chat syndrome