Achondroplasia is the most common form of short-limbed
dwarfism. It is characterized by short-limbed dwarfism, macrocephaly,
frontal bossing, a low nasal bridge, and midface hypoplasia. Skeletal
malformations may include brachydactyly, lordosis, genu varum, and/or
stenosis of the spine. Additional abnormalities may include limited
extension of the elbows and hips, hypotonia, and frequent otitis media. In
most cases achondroplasia appears sporadically.
Achondroplasia appears to occur
sporadically with no apparent family history. However, the possibility of
familial transmission has been suggested, and inheritance as an autosomal
dominant pattern with new dominant gene mutations has been reported.
Advanced paternal age may be a contributing factor in cases of sporadic
achondroplasia. In the absence of mutations, familial cases of
achondroplasia have been reported as autosomal dominant inheritance but are
much less common. Specific mutations of a gene known as fibroblast growth
factor receptor (FGFR)-3 are possible. The
FGFR-3 gene is located on chromosome 4 (4p16.3).
Achondroplasia is a rare genetic disorder
characterized by macrocephaly, frontal bossing, and depressed nasal bridge.
The arms and legs usually are very short, and the trunk appears long in
comparison. Rhizomelic dwarfism, unusually prominent abdomen and buttocks,
and short hands with fingers usually assuming a “trident" or three-pronged
position during extension are characteristic. The trident position is
described by an index and middle finger typically close together and the
ring finger and the pinkie close together, giving the hand a three-pronged
(trident) appearance. The hands are generally short and broad. Infants
typically have an arched or vaulted skull in response to the megaloencephaly,
which is pathognomonic of the syndrome. The forehead is broad. Midface
hypoplasia can be seen. The presence of dorsal kyphosis adds to the dwarfism
appearance. Hydrocephalus may be present, so the risk of elevated
intracranial pressure should be remembered. Compression of the brainstem
because of foramen magnum stenosis may occur in some children and result in
a life-threatening condition. The respiratory system may be associated with
upper airway obstruction because of midface hypoplasia and short neck. Other
features include hearing loss secondary to chronic recurrent otitis media.
The incidence of obstructive sleep apnea has been reported because of the
macroglossia, high arched palate, prominent mandible, and choanal stenosis.
Tonsilloadenoidectomy may improve the symptoms. The cardiovascular system is
not involved in this disease. However, as a result of airway obstruction,
secondary pulmonary artery hypertension and right ventricular hypertrophy
may develop. Obesity may develop in both genders. The mean male adult height
is 131 cm and the mean female height is 124 cm. Children may have
deformities of the rib cage, including excessive curvature or “cupping” of
the ribs. Intellectually, achondroplasia does not cause any impairment or
deficiencies in mental abilities. The life expectancy of infants older than
12 months is normal.
The presence of normal intelligence and
proper social skills for their age should be considered in the management of
the children, adolescents, and adults with the disorder. The most important
anesthetic consideration should be ...