Post-inflammatory hyperpigmentation is seen here in a mottled pattern, over the posterior shoulder. Hemosiderin, left behind by degraded RBC's, creates the discoloration.
Update Date 4/14/2015
Updated by: Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.