Prominent creases (called "flexion creases") appear on the palms of the hands and soles of the feet. The palm normally has three flexion creases. Sometimes, the two horizontal creases fuse to form a single crease, called a single palmar crease or a "simian crease."

Many structures develop in the fetus in the first few months of gestation. Palmar creases develop early, by the 11th to 12th week of life. Abnormalities in palmar creases may indicate problems with early development and be associated with other developmental disorders like Down's Syndrome.

However, a single palmar crease or simian crease appears in approximately 1 out of 30 people. Males are twice as likely as females to have this condition.

• normal finding (approximately 3% of the population)
• Down's syndrome
• Aarskog syndrome
• Cohen syndrome
• fetal alcohol syndrome
• trisomy 13
• rubella syndrome
• Turner's syndrome
• Klinefelter's syndrome
• pseudohypoparathyroidism
• gonadal dysgenesis
• cri du chat syndrome

An infant with a simian crease generally has other symptoms and signs that, when taken together, define a specific syndrome or condition. Diagnosis of that condition is based on a family history, medical history, and thorough physical evaluation.

Medical history questions documenting a simian crease in detail may include:

• Is there a family history of Down syndrome or other disorder associated with a simian crease?
• Have other family members had a simian crease and no other abnormality?
• What was the pregnancy like?
• Did the mother use alcohol while pregnant?
• What other symptoms or physical abnormalities are also present?

Note: This finding is usually discovered by the health care provider.

The history and physical examination findings will determine whether further laboratory and diagnostic procedures are necessary.