Rash orientation in pityriasis rosea: a qualitative study

Area of Science:

• Dermatology
• Clinical Anatomy
• Medical Education

Background:

• Pityriasis rosea (PR) rash orientation has been variably described, leading to potential confusion.
• Previous descriptions include Christmas-tree, inverted Christmas-tree, fir tree, and parallel to ribs patterns.
• A standardized description for PR rash orientation is needed for clarity in medical education.

Purpose of the Study:

• To qualitatively study the orientation of pityriasis rosea rashes.
• To determine the most accurate anatomical description for PR rash orientation.
• To advocate for a standardized descriptive term to improve clarity.

Main Methods:

• Qualitative study of rash orientation.
• Retrieved clinical photographs of 11 patients diagnosed with pityriasis rosea over two years.
• Analysis of rash patterns in relation to anatomical lines.

Main Results:

• The rash orientation in pityriasis rosea predominantly follows Langer's cleavage lines.
• All three components of Langer's lines (V-shaped, circumferential, transverse) were observed in most patients.
• Langer's cleavage lines provide a more accurate and consistent description than previously used patterns.

Conclusions:

• Langer's cleavage lines are the most appropriate description for pityriasis rosea rash orientation.
• The mechanism by which PR follows Langer's lines remains unknown.
• Abandoning ambiguous descriptions like "Christmas-tree pattern" is recommended to reduce confusion for students and physicians.