What is characterized by a single palm crease and is often associated with Down syndrome?

The term that refers to the presence of a single transverse line across the palm, often associated with Down syndrome, is the Simian crease. This anatomical variation is significant because it is an indicator that can correlate with certain genetic conditions, particularly Down syndrome, which is characterized by the presence of an extra chromosome 21.

The Simian crease results from the merging of the normal two primary palm creases into one single line, which can be used as a diagnostic clue in clinical settings. In patients who have Down syndrome, up to 50% exhibit this singular crease, making it a notable feature for clinicians to observe during physical examinations.

While the transverse palmar crease might seem similar, it specifically describes the single line that is sometimes included in the definition of the Simian crease, but the term Simian crease is more widely recognized in clinical contexts for its association with congenital conditions. Flexion creases and proximal palm creases do not provide the same diagnostic significance related to Down syndrome, and they refer to different aspects of the anatomy of the hand.