A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.[nb 1] They can be brown, purple, pink or red in color, and can cluster into a papular rash. The papules may open when scratched and become infected and crusty.
Papules may have different shapes and are sometimes associated with other features such as crusts or scales.
There are many skin diseases which develop papules, such as Lichen planus, a skin disease which classically forms polygonal, purple papules.
- ^ With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm, not 1cm, while others state an entirely different measurement. Therefore, for this article, the 1cm cutoff is used which is discussed in Andrews' Diseases of the Skin: Clinical Dermatology (see references), a work considered by some dermatologists as an authority on this subject matter. See Lack of Standardization for complete discussion.