What is the clinical significance of a single transverse palmar crease in a newborn?

A single transverse palmar crease, also known as a simian line, is characterized by the absence of the normal two creases that typically form on the palm. This particular trait has clinical significance and is often associated with certain chromosomal abnormalities, most notably Down syndrome (Trisomy 21).

The presence of a single transverse palmar crease can serve as a soft marker during a clinical assessment for Down syndrome, especially when it is found alongside other features such as hypotonia, epicanthic folds, or a gap between the first and second toes. Although this finding alone is not diagnostic for Down syndrome, it raises awareness and prompts further evaluation, such as genetic testing.

While it is true that a single transverse palmar crease is considered a normal genetic variation in some populations, its association with Down syndrome is particularly notable in clinical practice. Other conditions, such as congenital heart defects or limb malformations, do not have as strong of a correlation with this specific physical finding. Therefore, identifying a single transverse palmar crease can be significant in steering clinical assessments toward Down syndrome, leading to timely evaluation and interventions when appropriate.