Single transverse palmar crease
Other names	Simian crease, simian line
Single transverse palmar crease on an infant's hand
Specialty	Medical genetics

In humans, asingle transverse palmar crease is a single crease that extends across the palm of thehand, formed by the fusion of the twopalmar creases. Although it is found more frequently in persons with several abnormal medical conditions, it is not predictive of any of these conditions since it is also found in persons with no abnormal medical conditions.

This crease is estimated to occur in 1.5-3% of the general population, although it is more common in East Asian and Native American populations.^[1][2][3]

Because it resembles the usual condition of non-humansimians, it was, in the past, called thesimian crease orsimian line. These terms have widely fallen out of favor due to their pejorative connotation.^[4]

This crease is found in 45% of people withdown syndrome.^[5][2][3]

The presence of a single transverse palmar has been associated with several abnormal medical conditions—that is, it is found at a higher than 1.5% frequency, but in all of these conditions, many do not have this crease. Examples of conditions with such an association arefetal alcohol syndrome and the genetic chromosomal abnormalities, such asDown syndrome (chromosome 21),cri du chat syndrome (chromosome 5),Klinefelter syndrome,Wolf–Hirschhorn syndrome,Noonan syndrome (chromosome 12),Patau syndrome (chromosome 13),IDIC 15/Dup15q (chromosome 15),Edward's syndrome (chromosome 18), andAarskog–Scott syndrome (X-linked recessive), or autosomal recessive disorder, such asleukocyte adhesion deficiency-2 (LAD2).^[6] A unilateral single palmar crease was also reported in a case ofchromosome 9 mutation causingnevoid basal cell carcinoma syndrome andRobinow syndrome.^[7] It is also sometimes found on the hands of the affected side of patients withPoland syndrome andcraniosynostosis.

A 1971 study refutes the hypothesis that the phenomenon is caused by fetal hand movement: the appearance of the crease occurs around the second month of gestation before the digital movement phase in the womb begins.^[8]

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  Single transverse palmar crease in an adult
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  More common palmar creases in adults
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  Bilateral single transverse palmar crease. The single transverse palmar crease is present on both hands of the individual.

• Dermatoglyphics

• Hand
• Down syndrome

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• Articles with short description
• Short description is different from Wikidata
• Short description matches Wikidata
• Use dmy dates from April 2017