DWARFISM(ACHONDROPLASIA)

Gatbonton, Sharmhaine

Parrocha, DinahDMD 2D

ACHONDROPLASIA

Literally means “without cartilage formation”

Most common type of dwarfism.

Caused by mutation of gene for (FGFR3)

Average height is about 4 ft.

Short arms and legs.

Large head.

SIGNS AND SYMTOMS

Abnormal hand appearance with persistent space

between the long and ring fingers

Bowed legs

Decreased muscle tone

Disproportionately large head-to-body size

difference

Prominent forehead

Shortened arms and legs (especially the upper arm

and thigh)

Short stature (significantly below the average

height for a person of the same age and sex)

Spinal stenosis

Spine curvatures called kyphosis and lordosis

PATHOGENESIS

The gene affected is the Fibroblast Growth Factor

Receptor 3 Gene.

Achondroplasia gene was mapped near the telomere of

the short arm of chromosome 4.

The FGFR3 protein is involved in the development and

maintainance of bone and brain tissue.

Receptor regulates bone growth by limiting the formation

of bone from cartilage in the long bones.

DENTAL CORRELATION

The administration of thyroid hormone is known to

accelerate dental development and eruption.

his dental development is still extremely retarded

and is following a disturbed pattern in which various

stages of dental development are present

simultaneously.

For example, he shows absence of resorption of the

deciduous canine and deciduous molar roots, which

is found in children from the age of 8 onward. The

permanent second molars, which usually are erupted

at the age of 12 years, are still unerupted and have

cortical bone overlying their occlusal surfaces.

This is usually not found after the age of 12 years.

To the contrary, the third molars are located in the

body of the mandible, which is not frequently seen

before the age of 15 years.

MENDELIAN

It is inherited as a mendelian autosomal dominant

trait with complete penetrance. Approximately 80%

of cases are due to new or de novo dominant

mutations with a mutation rate estimated to be

0.000014 per gamete per generation.

SINGLE GENE

It is single gene because it only affects the

Fibroblast Growth Factor Receptor 3 Gene which is

responsible for the maintenace of bone and brain

tissue.