Achondroplasia is the
most common form of disproportionate short stature. The diagnosis
is based on very specific features on the radiographs, which include
a contracted base of the skull, a square shape to the pelvis with
a small sacrosciatic notch, short pedicles of the vertebrae, rhizomelic
(proximal) shortening of the long bones, trident hands, a normal
length trunk, proximal femoral radiolucency, and, by mid-childhood,
a characteristic chevron shape of the distal femoral epiphysis.
Hypochondroplasia and thanatophoric dysplasia are part of the differential
diagnosis, but Achondroplasia can be distinguished from these because
the changes in hypochondroplasia are milder and the changes in thanatophoric
dysplasia are much more severe and invariably lethal. Achondroplasia
is an autosomal dominant disorder, but approximately 75% of cases
represent new dominant mutations. The gene for Achondroplasia has
recently been found. Achondroplasia is due to a change in the genetic
information for fibroblast growth factor receptor 3.[2,3] Almost
all of the mutations have been found to occur in exactly the same
spot. Now that the gene has been found and the mutation known, potential
therapies and diagnostic methodologies are likely to be developed.
A great deal is known about the natural history of the disorder
that can be shared with the family. The average adult height in
Achondroplasia is about 4 ft for both men and women Other features
include disproportionate short stature, with shortening of the proximal
segment of the limbs, a prominent forehead, a flattened midface,
and an average-sized trunk. The head usually appears relatively
large compared with the body. The most common complication, occurring
in adulthood, is related to lumbosacral spinal stenosis with compression
of the spinal cord or nerve roots. This complication is usually
treatable by surgical decompression, if diagnosed at an early stage.
Children affected with Achondroplasia frequently have delayed motor
milestones, otitis media, and bowing of the knees Occasionally in
infancy or early childhood there is symptomatic airway obstruction,
development of thoracolumbar kyphosis, symptomatic hydrocephalus,
or symptomatic upper cord compression. Most individuals with Achondroplasia
are of normal intelligence and are able to lead independent and
productive lives. Because of their disproportionate short stature,
however, a number of psychosocial problems can arise. Families can
benefit from anticipatory guidance and the opportunity to learn
from other families with children of disproportionate short stature.
' Myrhe of 1 year old Copyright 2007'
The following guidelines are designed to help the pediatrician care
for children with Achondroplasia and their families. Issues that
need to be addressed at various age groups are discussed ( Table).
These guidelines are not appropriate for other chondrodysplasias,
because each type has its own natural history, complications, and
specific guidelines. It is important that parents also consult a
physician with experience and expertise concerning Achondroplasia
early in their child's development, because these guidelines are
intended for the general pediatrician without such experience.
Pseudoachondroplasia, a short-limbed dwarfism, is inherited in an
autosomal dominant fashion. Clinically, it has little resemblance
Pediatricians may be called upon to counsel a family in which a
fetus has Achondroplasia or is suspected to have Achondroplasia.
In some settings, the pediatrician will be the primary resource
for counseling a family. At other times, counseling may already
have been provided to the family by a clinical geneticist and/or
the obstetrician. Because of a previous relationship with the family,
however, the pediatrician may be called on to review this information
and to assist the family in the decision-making process.
of Achondroplasia in the fetus is most often only made with certainty
when one or both parents have this condition. In this circumstance
the parents are usually knowledgeable about the disorder, the inheritance,
and the prognosis for the offspring.
situations in which the parents have normal stature, the diagnosis
may only be suspected based on the observation of disproportionately
short limbs in the fetus by ultrasound. With the frequent use of
ultrasound, approximately one third of cases of fetal Achondroplasia
are suspected prenatal. However, disproportionately short limbs
are observed in a heterogeneous group of conditions. In the majority
of these cases, the specific diagnosis cannot be made with certainty
except by radiography late in pregnancy or more usually after birth.
In these cases, caution should be exercised when counseling the
family. In those infrequent cases in which the diagnosis is unequivocally
established either because of the familial nature of the disorder
or by prenatal radiography, the pediatrician may discuss the following
issues as appropriate.
confirm, and demonstrate laboratory or imaging studies leading to
the mechanisms for occurrence or recurrence of Achondroplasia in
the fetus and the recurrence risk for the family.
least 75% of cases of Achondroplasia occur in families in which
both parents have average stature and Achondroplasia in the offspring
occurs due to sporadic mutation in the gene.
the natural history and manifestations of Achondroplasia, including
further studies that should be done, particularly those to confirm
the diagnosis in the newborn period. If miscarriage, stillbirth,
or termination occurs, confirmation of diagnosis is important for
counseling family members about recurrence.
the currently available treatments and interventions. This discussion
needs to include the efficacy, complications, side effects, costs,
and other burdens of these treatments. Discuss possible future treatments
the options available to the family for the management and rearing
of the child using a nondirective approach. In cases of early prenatal
diagnosis, these may include discussion of pregnancy termination,
as well as continuation of pregnancy and rearing of the affected
child at home, foster care, or adoption. When both parents are of
disproportionate short stature, the possibility of double heterozygosity
or homozygosity for Achondroplasia must be assessed. Infants with
homozygous Achondroplasia usually are either stillborn or die shortly
after birth. Homozygous Achondroplasia can usually be diagnosed
the mother is affected with Achondroplasia, a cesarean section must
be performed because of a small pelvis. This surgical procedure
usually involves general anesthesia because of the mother's spinal
stenosis and the consequent risk associated with conduction (spinal/epidural)
anesthesia. A mother affected with Achondroplasia may develop respiratory
compromise in the third trimester of pregnancy, so baseline pulmonary
function studies should be done. A pregnancy at risk for homozygosity
should be followed with ultrasound measurements at 14, 16, 18, 22,
and 32 weeks of gestation in order to distinguish homozygosity or
heterozygosity from normal growth patterns in the the fetus. New
DNA diagnostic studies are likely to become available
short limb dwarfism
The information provided on this site is designed to support,
not replace, the relationship that exists between a patient/site
visitor and his/her existing physician/Doctor.