urticaria pigmentosa

[pĭg′mən-tōsə]
n.
  1. Mastocytosis resulting from congenital excess of mast cells in the superficial dermis and characterized by brownish papules that urticate when stroked.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.