This is a picture of microscopic polyarteritis on the shin. The term polyarteritis means that many blood vessels are inflamed. These nodules are located just below the skin's surface (subcutaneous), are barely felt when pressing on the skin (palpable), and are tender. The skin is typically red (erythematous).
Review Date 1/10/2019
Updated by: Gordon A. Starkebaum, MD, MACR, ABIM Board Certified in Rheumatology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.