The presence of a<unk>  has no medical significance. It is found in 1.5% of all persons, and though it is found at a higher frequency in persons with abnormal medical conditions, in every one of these conditions many persons do not have a<unk> , thus it has low predictive value. 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. While it is often found in persons with Down Syndrome, many who have this syndrome do not have this<unk> , and thus is not a diagnostic indicator of the Down Syndrome. The presence of a<unk><unk><unk>  has been associated with a number of 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<unk> . Examples of conditions with such an association are fetal alcohol syndrome, and with the genetic chromosomal abnormalities Down 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), and Aarskog-Scott syndrome (X-linked recessive), or autosomal recessive disorder, such as Leukocyte adhesion deficiency-2 (LAD2). A unilateral<unk><unk><unk>  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. A 1971 study refutes the hypothesis that the phenomenon is caused by fetal hand movement: the appearance of the<unk>  occurs around the second month of gestation, before the digital movement phase in the womb begins. Image:Single<unk><unk><unk>  adult.Single<unk><unk><unk>  in an adult Image:Normal<unk> s adult.More common<unk><unk> s in adults
Single transverse palmar crease
Clinodactyly
Pachydermodactyly
Sclerodactyly
Oligodactyly
Ectrodactyly
Polydactyly
Synpolydactyly