A single palmar crease is a single line that runs across the palm of the hand. People most often have 3 creases in their palms.

The crease is most often referred to as a single palmar crease. The older term "simian crease" is not used much anymore, since it tends to have a negative meaning (the word "simian" refers to a monkey or ape).

Transverse palmar crease; Palmar crease; Simian crease

Distinct lines that form creases appear on the palms of the hands and soles of the feet. The palm has 3 of these creases in most cases. But sometimes, the creases join to form just one.

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

A single palmar crease appears in about 1 out of 30 people. Males are twice as likely as females to have this condition. Some single palmar creases may indicate problems with development and be linked with certain disorders.

Having a single palmar crease is often normal. However, it may also be associated with various conditions that affect a person's mental and physical growth, including:

• Down syndrome
• Aarskog syndrome
• Cohen syndrome
• Fetal alcohol syndrome
• Trisomy 13
• Rubella syndrome
• Turner syndrome
• Klinefelter syndrome
• Pseudohypoparathyroidism
• Cri du chat syndrome

An infant with a single palmar crease may have 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 complete physical exam.

Your health care provider may ask questions such as:

• Is there a family history of Down syndrome or other disorder associated with a single palmar crease?
• Does anyone else in the family have a single palmar crease without other symptoms?
• Did the mother use alcohol while pregnant?
• What other symptoms are present?

Based on the answers to these questions, the medical history, and the results of the physical exam, further testing may be necessary.

Published Date: April 05, 2025
Published By: Charles I. Schwartz, MD, FAAP, Clinical Assistant Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, General Pediatrician at PennCare for Kids, Phoenixville, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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