Hypertrophic Response and Keloid Diathesis: Two Very Different Forms of Scar

Background: Hypertrophic and keloid scars remain extremely challenging, particularly in their variable response to treatment. The understanding of hypertrophic and keloid scarring is evolving from a position where they were regarded as different stages of the same process to the contemporary perspective of two separate entities. This article reviews the differences in the two forms of scarring and discusses the implications for future research. Methods: The authors conducted a MEDLINE search of all English language reviews linking key words "hypertrophic," "keloid," and "scarring." Results: Over the past four decades, there has been considerable clinical and experimental research looking at the biological nature and therapeutic response of keloid and hypertrophic scarring. As more differences are emerging regarding the fundamental biology of the scars, investigators are giving more detailed characterization of their source material. It is evident that even within the broad categories of hypertrophic and keloid scarring there is a heterogenous distribution of pathologic con-nective tissue matrix biology. Conclusion: Considerable advances have been made in our understanding of the fundamental biology of scarring. As research methodology becomes even more sophisticated, it will be even more crucial to extensively characterize source material, recognizing major differences not only between keloid and hypertrophic scar but also between scars of varying stages of maturation and histomorphological, biochemical, and molecular variations within individual scars. (Plast. Reconstr. Surg. 116: 150e, 2005.)