Single transverse palmar crease
|Single transverse palmar crease|
Single transverse palmar crease on an infant's hand
|Classification and external resources|
|ICD-9||757.2 (CDC/BPA 757.200)|
In humans, a single transverse palmar crease is a single crease that extends across the palm of the hand, formed by the fusion of the two palmar creases (known in the pseudoscience of palmistry as the "heart line" and the "head line") is found in half of people with Down Syndrome. It is also found in 10% of the general population.
Because it resembles the usual condition of non-human simians, it is also known as a simian crease or simian line, although these terms have widely fallen out of favor due to their pejorative connotation.
Single palmar creases are less common than two palmar creases, however 10% of the population have one palmar crease on one hand and 5% have one palmar crease on both hands. It is sometimes associated with Down syndrome, though other physical symptoms would be manifest with this relatively rare syndrome. 
Males are twice as likely as females to have this characteristic, and it tends to run in families. In its non-symptomatic form, it is more common among Asians and Native Americans than among other populations, and in some families there is a tendency to inherit the condition unilaterally, that is, on one hand only.
The presence of a single transverse palmar crease can be, but is not always, a symptom associated with abnormal medical conditions, such as fetal alcohol syndrome, or with genetic chromosomal abnormalities, including Down Syndrome (chromosome 21), cri du chat syndrome (chromosome 5), Klinefelter syndrome, Wolf-Hirschhorn Syndrome, Noonan syndrome (chromosome 12), Patau syndrome (chromosome 13), Edward's syndrome (chromosome 18), and Aarskog-Scott syndrome (X-linked recessive). A unilateral single palmar crease was also reported in a case of chromosome 9 mutation causing Nevoid basal cell carcinoma syndrome and Robinow syndrome. It is also sometimes found on the hand of the affected side of patients with Poland Syndrome and craniosynostosis.
- McPherson M.D., Katrina (2004-05-03). "Simian crease". Medical Encyclopedia. United States National Library of Medicine. Retrieved 2006-09-28.
- "Definition of Simian crease". MedicineNet. MedicineNet, Inc. 2005. Retrieved 2006-09-28.
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