Webster's New World Medical Dictionary

ptosis
Downward displacement. For example,
ptosis of the eyelids is drooping of the eyelids.
ptosis of the eyelids, congenital
See 
congen-
ital ptosis of the eyelids.
P
-
24 antibody
An antibody that is created by B
cells in the immune system to fight the P-24 antigen
of the HIV virus. The P-24 antibody attaches to the
foreign protein and sends a signal to T-4 cells to
attack it. See also 
HIV; P
-
24 antigen.
P
-
24 antigen
A structural protein that is found
only in the HIV virus. Tests for the level of P-24 anti-
gen may be done to detect early HIV infection and to
screen donated blood for the presence of HIV. P-24
antigen is only detectable during a limited period of
time; after the infection has established itself and
antibodies have been produced, levels of P-24 anti-
gen usually are not detectable. See also 
HIV; HS test;
P
-
24 antibody.
pubarche
The onset of puberty, often measured
by the first development of pubic hair.
puberty
Adolescence, the period in which the
human body first becomes capable of reproduction.
The timing of the development of puberty is variable
and involves many factors including genetic, nutri-
tional, environmental, and social factors.
pubic lice
Parasitic insects found in the genital
area of humans. Pubic lice are usually spread
through sexual contact. Rarely, infestation can be
spread through contact with an infested person’s
bed linens, towels, or clothes. Pubic lice are gener-
ally found in the genital area on pubic hair but may
occasionally be found on other coarse body hair,
such as hair on the legs, armpit, mustache, beard,
eyebrows, and eyelashes. Lice found on the head are
not pubic lice; they are head lice. Animals do not get
or spread pubic lice. The key symptom of pubic lice
is itching in the genital area. Nits (lice eggs) or
crawling lice may be seen. Pubic lice are treated
with topical medications such as permethrin or
Lindane. Also known as crabs.