Webster's New World Medical Dictionary

retinitis pigmentosa and deafness
See
Usher syndrome.
retinoblastoma
A malignant eye tumor usually
seen in children, that arises in cells in the develop-
ing retina that contain cancer-predisposing muta-
tions in both copies of the gene RB1. Abbreviated
RB. The most common sign of RB is a white pupil-
lary reflex to light (leukocoria). There are two
forms of RB: hereditary and sporadic. The inherited
form of RB is usually present at birth as multiple
tumors in both eyes. It is due to the transmission of
an RB1 germline mutation followed by an acquired
somatic RB1 mutation. The sporadic form of
retinoblastoma has later onset and typically leads to
a single tumor in only one eye. It is due to acquired
mutations in both RB1 genes. Patients with heredi-
tary RB are at increased risk of developing tumors
outside the eye, including pinealomas (in the pineal
gland of the brain), osteosarcomas, soft tissue sar-
comas, and melanomas. When RB is detected at an
early stage, it can sometimes be treated locally but
often requires removal of the eye (enucleation).
Early diagnosis and treatment of RB and RB-related
tumors reduces morbidity and increases longevity.
retinoic acid syndrome
A disorder due to the
cancer treatment retinoic acid characterized by
fever, difficulty breathing, chest pain, lung infiltrates,
fluid around the lungs and heart, and hypoxia (lack
of oxygen) that develops in some patients receiving
retinoic acid therapy. It usually develops within 30
days of treatment. Steroids and chemotherapy can be
used to treat retinoic acid syndrome.
retinol
Vitamin A. See also Appendix C,
“Vitamins.”
retinopathy
Any disease of the retina, the light-
sensitive membrane at the back of the eye. The type
retardation, mental
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of retinopathy is often specified, such as arterioscle-
rotic retinopathy, diabetic retinopathy, or hyperten-
sive retinopathy.