Very rare disorder characterized by extreme
short-limbed dwarfism, lack of development of ribs, and other major bone
formation. There are several subtypes of achondrogenesis. In general these
forms are characterized by premature birth, fetal hydrops, normocephaly but
an unusually soft cranial vault, and a short neck and trunk. Affected
individuals have extremely short limbs, ribs, and vertebra. The disorder
often is life-threatening either in utero or shortly after birth.
Chondrogenesis Imperfecta; Hypochondrogenesis;
Lethal Neonatal Dwarfism; Lethal Osteochondrodysplasia; Neonatal Dwarfism.
Five subtypes of achondrogenesis have been
Houston-Harris Type, achondrogenesis (type IA)
Parenti-Fraccaro Type, achondrogenesis (type IB)
Langer-Saldino Type, achondrogenesis (type II)
Achondrogenesis, Type III
Achondrogenesis, Type IV
Achondrogenesis can be inherited as an autosomal or dominant recessive
genetic trait. Achondrogenesis types IA, III, and IV are believed to be
inherited as an autosomal recessive genetic trait. Achondrogenesis type IB
is inherited as an autosomal recessive genetic trait with significant
mutations in a gene called the diastrophic dysplasia/sulfate transporter gene.
This gene encodes a sulfate transporter
(DTDST). In addition, a deficiency in an enzyme responsible for the biologic
activation of sulfate in children with type IB has been suggested.
Achondrogenesis type II may be inherited by an autosomal recessive or
dominant genetic trait. The possibility of mutations of the gene (COL2A1)
encoding type II collagen has been suggested.
There are several types of
achondrogenesis. In general they are characterized by premature birth, fetal
hydrops, normocephaly with cranial vault softness, and a short neck and
trunk. Affected individuals have extremely short limbs, ribs, and vertebra,
and other bones of the skeleton are not properly developed. Infants usually
are born with a very prominent abdomen. Other features include a cleft
palate, corneal clouding, ear deformities, and underdeveloped testicles and
- Achondrogenesis type I affects individuals with abnormally small or short bones in
the arms and/or legs (micromelia). The patient's head is normal, but the
calvarial plates may be unusually soft. The two subtypes of achondrogenesis
type I are Houston-Harris type IA and Parenti-Fraccaro type IB. The Houston-Harris type
is characterized by premature birth, fetal hydrops, and
polyhydramnios. After birth, the affected infant usually manifests
micrognathia, low-bridged nose, extreme short stature that is identifiable
at birth, very short limbs (micromelia), lack of development of the bones of
the spine, and an extremely short neck. The infant usually is stillborn or
dies shortly after birth. The Parenti-Fraccaro type is characterized by the presence of thin ribs
subjected to spontaneous fractures during manipulation at birth. The patient
presents as a short-limbed dwarf in whom the important short stature and
short limb disorder is easily identifiable at birth. The respiratory system
often is affected by respiratory insufficiency resulting from pulmonary
hypoplasia. The child is born prematurely and most often presents a fetal
hydrops. The skeleton system is significantly affected with inappropriate
development, especially of the spine, arms and legs. The infants ...
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