Dictionary

phenocopy 1 An environmental condition that imitates a condition that is produced by a gene. 2 A person who has an environmental condition that mimics a condition that is produced by a gene.

phenomenon, Babinski See Babinski reflex.

pervasive developmental disorder Abreviated PDD, one of a group of disorders characterized by delays in the development of multiple basic functions including socialization and communication. Parents may note symptoms as early as infancy and typically onset is prior to 3 years of age. Symptoms may include communication problems such as using and understanding language; difficulty…

pes Latin word meaning foot.

pes cavus A foot with an arch that is too high.

pes planus Flatfoot.

pest See plague.

pestilence 1 Originally, bubonic plague. See also plague. 2 Any epidemic disease that is highly contagious, infectious, virulent, and devastating.

pestis See plague.

PET scan Positron emission tomography scan, a highly specialized imaging technique that uses short-lived radioactive substances. This technique produces three-dimensional colored images. Unlike computerized tomography (CT) and magnetic resonance imaging (MRI), which look at anatomy or body form, PET studies metabolic activity or body function. PET scanning has been used primarily to evaluate problems of…

petechiae Tiny red spots in the skin or mucous membranes that do not blanch when pressed upon and that result from blood leaking from capillaries. The causes of petachiae include use of aspirin or other medications, allergic reactions, autoimmune disease, viral infection, thrombocythemia (an abnormally high platelet level), idiopathic thrombocytopenic purpura (ITP), leukemia and other…

petit mal See seizure, absence; seizure disorder.