A simian crease is a single line that runs across the palm of the hand. People usually 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 referred to as a single palmar crease.
Strong lines (called palmar flexion creases) appear on the palms of the hands and soles of the feet. The palm usually 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.
A single palmar crease is often a normal finding. However, it may also be associated with:
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 doctor may ask questions such as:
Based on the answers to these questions, the medical history, and the results of the physical exam, further testing may be necessary.
Single palmar crease; Transverse palmar crease; Palmar crease
Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.
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