Webster's New World Medical Dictionary

rickettsiosis
Infection with Rickettsia. See also
Rickettsia.
rickettsiosis, North Asian tick-borne
One of
the tick-borne rickettsial diseases of the eastern
hemisphere, similar to but less severe than Rocky
Mountain spotted fever. Symptoms include fever, a
small ulcer (eschar) at the site of the tick bite,
swollen glands near the site of the bite (satellite
lymphadenopathy), and a red, raised (maculopapu-
lar) rash.
right heart
See 
heart, right.
right ventricle
See 
ventricle, right.
ring, intrastromal corneal
See 
intrastromal
corneal ring.
ring chromosome
A structurally abnormal chro-
mosome in which the end of each chromosome arm
has been lost and the broken arms have been
reunited to form a ring. A ring chromosome is
denoted by the symbol r.
ringworm
A fungal infection of the skin previ-
ously thought to be due to a parasite (worm). The
medical term for ringworm is tinea. The skin infec-
tions are sometimes characterized by round lesions
in the upper layers of the skin. Fungi that cause
ringworm are known as dermatophytes. See also
tinea barbae; tinea capitis; tinea corporis.
ringworm of the nails
See 
onychomycosis.
RIRS
Retrograde intrarenal surgery.
risk, obesity-related
See 
obesity-related 
disease.
risk factor
Something that increases a person’s
chances of developing a disease. For example, ciga-
rette smoking is a risk factor for lung cancer, and
obesity is a risk factor for heart disease.
risk of recurrence
See 
recurrence risk.
ritonavir
A medication (brand name: Norvir) in
the protease inhibitor family that is used to treat HIV
infection (AIDS). See also 
protease inhibitor.