The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.

DEFINITION:

purpura

1. A small hemorrhage (up to about 1 cm in diameter) in the skin, mucous membrane, or serosal surface, which may be caused by various factors, including blood disorders, vascular abnormalities, and trauma. Purpuric lesions may be associated with inflammation, in which case they present as papular purpura, or the hemorrhage may not be accompanied by inflammation, in which case they are macular.
2. Group of hemorrhagic diseases characterized by the presence of purpuric lesions, ecchymoses, and a tendency to bruise easily, which may be caused by decreased platelet counts, the presence of abnormal platelets, vascular defects, or reactions to certain drugs.