A simian crease is a single line that runs across the palm of the hand. People usually have 3 creases in their palms.
The 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). The crease is usually just referred to as a single palmar crease.
Single palmar crease; Transverse palmar crease; Palmar crease
Distinct lines that form creases appear on the palms of the hands and soles of the feet. The palm usually has 3 of these creases. But sometimes, the creases join together to form just one.
Palmar creases develop while a baby is growing in the womb, usually 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:
What to Expect at Your Office Visit
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.
Marcdante KJ, Kliegman RM. The approach to the dysmorphic child. In: Marcdante KJ, Kliegman RM. Nelson Essentials of Pediatrics. 7th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 50.
Nussbaum RL, McInnes RR, Willard HF. The chromosomal and genomic basis of disease. In: Thompson & Thompson Genetics in Medicine. 8th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 6.
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.