Webster's New World Medical Dictionary

ataxia-telangiectasia
A progressive disease char-
acterized by degeneration of the nervous system man-
ifest by poor coordination and balance (cerebellar
ataxia), red eyes due to widening of small blood ves-
sels in the conjunctiva (ocular telangiectasia), and
recurrent sinus and lung infections. Abbreviated AT.
Patients with AT have a striking predisposition to
leukemia and lymphoma and are extremely sensitive
to radiation. Other features include difficulty swal-
lowing and slowed growth. AT is inherited as an auto-
somal recessive trait. 
ATCC
American Type Culture Collection.
atelectasis
Failure of full expansion of the lung at
birth, or lung collapse thereafter. Also known as
collapsed lung.
atelectasis, primary
Failure of full expansion of
the lung at birth.
atelectasis, secondary
Partial or complete col-
lapse of a previously expanded lung. Secondary
atelectasis may occur when full chest expansion is
difficult, such as after chest surgery.
athelia
Absence of the nipple. Athelia tends to
occur on one side (unilaterally) in children with the
Poland syndrome and on both sides (bilaterally)
with certain types of ectodermal dysplasia. Athelia
also occurs in association with progeria (premature
aging). See also 
amastia; amazia; Poland syn-
drome; progeria.
atherectomy
A procedure to remove plaque
(atheroma) from the inside of a blood vessel.
Atherectomy is done most often in major arteries,
such as the coronary, carotid, and vertebral arter-
ies, that have experienced the occlusive effects of
atherosclerosis. Atherectomy may be accomplished
by various means, including angioplasty, laser sur-
gery, conventional surgical incision, or use of a
small drill-tipped catheter. In the US, atherectomy is
nicknamed the “Rotorooter” procedure, after a
company that cleans out drainage pipes.
atheroma
A fatty deposit in the inner lining
(intima) of an artery, resulting from atherosclero-
sis. Also called an atherosclerotic plaque, an arte-
rial plaque, or a plaque.
atherosclerosis
The presence of fatty lipid
deposits in the lining (intima) of an artery.
Atherosclerosis is a form of arteriosclerosis. See
also 
arteriosclerosis.
atherosclerotic
Pertaining to atherosclerosis.
Atherosclerotic heart disease is the leading cause of
death in the US. See 
atherosclerosis.
athetosis
Involuntary writhing movements, par-
ticularly of the arms and hands. Athetosis is associ-
ated with several neurological disorders, such as
cerebral palsy and Rett syndrome.