The Harlequin phenomenon.

Area of Science:

• Dermatology
• Pediatrics
• Neurology

Background:

• The Harlequin phenomenon (HF) is a rare condition characterized by abrupt, temporary, and distinct skin color changes.
• It typically presents as a midline demarcation, creating two different colored body halves.
• HF is most commonly observed in newborns but can occur in other age groups.

Purpose of the Study:

• To describe the Harlequin phenomenon, its clinical presentation, and potential underlying mechanisms.
• To differentiate between Harlequin phenomenon in newborns and older individuals.
• To emphasize the importance of investigating underlying causes in non-neonatal cases.

Main Methods:

• Clinical observation and case review.
• Review of existing literature on Harlequin phenomenon.
• Analysis of potential pathophysiological mechanisms, including sympathetic nervous system involvement.

Main Results:

• Harlequin phenomenon in newborns is often generalized or localized, attributed to immature hypothalamic control of sympathetic vascular tone.
• In older individuals, HF is typically localized to the face and neck and frequently associated with sympathetic disautonomy.
• While benign in neonates, HF in other age groups necessitates a thorough search for an underlying etiology.

Conclusions:

• Harlequin phenomenon in newborns is generally a benign, self-limiting condition.
• The presentation of Harlequin phenomenon in older individuals suggests a potential underlying neurological or autonomic disorder.
• Prompt medical evaluation is crucial for Harlequin phenomenon presenting outside the neonatal period.