pigmentation The coloring of the skin, hair, mucous membranes, and retina of the eye. Pigmentation is due to the deposition of the pigment melanin, which is produced by specialized cells called melanocytes. Other pigment-related terms include hyperpigmentation (too much pigment), hypopigmentation and underpigmentation (too little pigment), and depigmentation (loss of pigment).
pigment A substance that gives color to tissue. Pigments are responsible for the colors of skin, eyes, and hair.
pigeon breast Having a prominent breastbone and chest. Also known as pectus carinatum.
PID Pelvic inflammatory disease.
Pickwickian syndrome A syndrome that is characterized by obesity, sleepiness, hypoventilation, and a reddened face. It occurs because of reduced blood oxygen levels due to breathing insufficiency. The syndrome is named for the “fat and red-faced boy in a state of somnolency” whom Charles Dickens described in his novel The Pickwick Papers. Also known as…
Pick disease A form of dementia that is characterized by a slowly progressive deterioration of social skills and changes in personality, along with impairment of intellect, memory, and language. The common symptoms include loss of memory, lack of spontaneity, difficulty in thinking or concentrating, and disturbances of speech. Other symptoms can include gradual emotional dullness,…
pica A craving for something that is not normally regarded as nutritive, such as dirt, clay, paper, or chalk. Pica is a classic clue to iron deficiency in children, and it may also occur with zinc deficiency. Pica is also seen as a symptom in several neurobiological disorders, including autism and Tourette’s syndrome, and it…
pianist’s cramp A dystonia that affects the muscles of the hand and sometimes the forearm, and that only occurs when one plays the piano or another keyboard instrument. Similar focal dystonias have also been called writer’s cramp, typist’s cramp, musician’s cramp, and golfer’s cramp.
pia mater One of the meninges, the delicate innermost membrane that envelopes the brain and spinal cord. Known informally as the pia. See also meninges.
phytonutrient See phytochemical.
phytochemical A plant compound that is thought to have health-protecting qualities. Also known as phytonutrient.
phytanic acid storage disease See Refsum disease.