Webster's New World Medical Dictionary

Landau-Kleffner syndrome
A disorder with
onset in childhood characterized by the loss of
speech and recognition of spoken language.
Patients may also have behavioral disorders and
seizures and may develop behaviors similar to
autism. See also 
autism; epilepsy; seizure; seizure
disorder.
Landing disease
See 
GM1-gangliosidosis.
Langerhans cell histiocytosis
The preferred
name for what was once called histiocytosis X.
Langerhans cell histiocytosis refers to several disor-
ders in which histiocytes start to multiply and pro-
liferate abnormally. The result can be tissue
damage, pain, the development of tumor-like lumps,
fatigue, and other symptoms. If histiocytosis affects
the pituitary gland, diabetes insipidus may also
develop. Treatment includes radiation and
chemotherapy; although for reasons unknown,
some cases of histiocytosis go into remission with-
out treatment. This disease includes the conditions
known as eosinophilic granuloma, Letterer Siwe
disease, and Hand-Schuller-Christian disease.
Langerhans, islet of
See 
islet of Langerhans.
lanugo
Downy hair on the body of a fetus or new-
born baby. Lanugo is the first hair to be produced by
the fetal hair follicles, and it usually appears on the
fetus at about 5 months of gestation. Lanugo is very
fine, soft, and usually unpigmented. Although
lanugo is normally shed before birth, around 7 or 8
months of gestation, it is sometimes present at birth.
This is not a cause for concern: Lanugo disappears
of its own accord within a few days or weeks.
laparoscopy
A type of surgery in which small
incisions are made in the abdominal wall through
which a laparoscope and other instruments can be
placed to permit structures within the abdomen and