Webster's New World Medical Dictionary

Legg-Calvé-Perthes disease
A hip disorder in
children that is due to interruption of the blood sup-
ply to the head of the femur (the ball in the ball-
and-socket hip joint), causing it to deteriorate. This
disease is most common between ages 6 and 9, and
it tends to affect boys most commonly but is more
severe when it occurs in girls. Legg-Calvé-Perthes
disease sometimes runs in families. The symptoms
include hip and thigh pain, stiff hip, a limp, and
diminution in size of the thigh. Over a period of 18
to 24 months, the blood supply usually reestablishes
itself. During this period, the bone is soft and liable
to fracture under pressure, causing collapse of the
head of the femur. Treatment may include casting,
bracing, surgery, and physical therapy. Also known
as Legg disease, Legg-Perthes disease, Perthes dis-
ease, and avascular necrosis of the femoral head.
Legg-Perthes disease
See 
Legg-Calvé-Perthes
disease.
Legionella
The bacterium that causes
Legionnaires’ disease.
Legionnaires’ disease
A disease that is caused
by bacteria found in plumbing, shower heads, and
water-storage tanks. The disease was first identified
241
Legionnaires’ disease
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at the 1976 American Legion convention, and sub-
sequent outbreaks have occurred. The bacterium
that causes it, now known as Legionella, thrives in
the mist of condensers, air conditioners, and evap-
orative cooling towers, and it can infest an entire
building or airplane. The symptoms of Legionnaires’
disease are much like those of pneumonia and can
be overwhelming and sometimes fatal. Also known
as Legionella pneumonia.
Leigh’s disease
A rare, inherited disorder char-
acterized by degeneration of the central nervous
system. Leigh’s disease can be caused by mutations
in mitochondrial DNA or by deficiencies of an
enzyme called pyruvate dehydrogenase. Symptoms
usually begin between the ages of 3 months and 2
years and progress rapidly. Early symptoms may
include poor sucking ability and loss of head con-
trol and motor skills, loss of appetite, vomiting, irri-
tability, continuous crying, and seizures. As the
symptoms progress, weakness, lack of muscle tone,
and episodes of lactic acidosis, which can lead to
impairment of respiratory and kidney function, may
occur. The prognosis is poor.