Single transverse palmar crease


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. It is often found in Down Syndrome, but is not necessarily an indication that a person with single transverse palmar crease has the condition. It is only found in 1.5% of the world population in at least one hand.
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.

Medical significance

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, cri du chat syndrome, Klinefelter syndrome, Wolf-Hirschhorn Syndrome, Noonan syndrome, Patau syndrome, IDIC 15/Dup15q, Edward's syndrome, and Aarskog-Scott syndrome, or autosomal recessive disorder, such as Leukocyte adhesion deficiency-2. 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.