Achondroplasia: A Genetic Disorder

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Questions and Answers

What is the name of the gene responsible for encoding a protein that plays a crucial role in bone growth and maintenance?

FGFR3 (correct)

FGFR2

FGFR1

FGFR4

What is the mode of inheritance of achondroplasia?

Mitochondrial

Autosomal recessive

Autosomal dominant (correct)

X-linked

What is the effect of the mutation in the FGFR3 gene on chondrocytes?

It inhibits their proliferation and maturation (correct)

It increases their apoptosis

It stimulates their proliferation and maturation

It has no effect on them

What is the percentage of cases where achondroplasia results from new (de novo) mutations?

80% Signup and view all the answers

What happens if both parents have achondroplasia?

The child has a 75% chance of inheriting the condition Signup and view all the answers

What is the role of the FGFR3 protein in the body?

It acts as a receptor that transmits signals to cells to regulate their growth and division Signup and view all the answers

What is the chance of a child inheriting achondroplasia if one parent has the condition?

50% Signup and view all the answers

What is the fate of a child who inherits two copies of the mutated FGFR3 gene?

The child will usually die shortly after birth Signup and view all the answers

What is the effect of FGFR3 activation on chondrocytes in endochondral bone?

It inhibits proliferation of chondrocytes Signup and view all the answers

What is the characteristic feature of the forehead in individuals with achondroplasia?

It is larger than normal Signup and view all the answers

What is the result of inhibition of cartilage during early development?

Shortened and improperly formed bones Signup and view all the answers

What is midface hypoplasia?

An underdeveloped midfacial region Signup and view all the answers

What is the purpose of monitoring growth patterns in individuals with achondroplasia?

To identify the disorder Signup and view all the answers

What is the characteristic feature of the nasal bone in individuals with achondroplasia?

It is flat Signup and view all the answers

What is the role of FGFR3 in endochondral bone?

It coordinates growth and differentiation of chondrocytes and bone progenitor cells Signup and view all the answers

What is the characteristic feature of the hands and feet in individuals with achondroplasia?

They are short Signup and view all the answers

What is the main purpose of genetic testing for achondroplasia?

To detect mutations in the FGFR3 gene Signup and view all the answers

What is the result of midface hypoplasia in achondroplasia?

A concave facial profile Signup and view all the answers

What is the implication of delayed dental development in achondroplasia?

Slower eruption of primary and permanent teeth Signup and view all the answers

What is the primary cause of achondroplasia?

Mutations in the FGFR3 gene Signup and view all the answers

What is the purpose of monitoring height, weight, and head circumference in infancy?

To track growth progress Signup and view all the answers

What is the result of dental crowding in achondroplasia?

Reduced space in the upper jaw Signup and view all the answers

What is the purpose of Non-Invasive Prenatal Testing (NIPT)?

To detect FGFR3 mutations associated with achondroplasia Signup and view all the answers

What is the type of malocclusion commonly associated with achondroplasia?

Class III malocclusion (underbite) Signup and view all the answers

What is characterized by constricted upper and lower dental arches?

Narrow Dental Arches Signup and view all the answers

What can affect speech and feeding?

High-Arched Palate Signup and view all the answers

What is a problem with how the teeth come together?

Bite Issues Signup and view all the answers

What is associated with dental crowding and malocclusion?

Airway Obstruction Signup and view all the answers

What is crucial for comprehensive care?

Interdisciplinary Approach Signup and view all the answers

What may be necessary to correct jaw alignment in severe cases of malocclusion and maxillary hypoplasia?

Orthognathic Surgery Signup and view all the answers

What is a management strategy to address the narrow maxilla and improve dental arch space?

Maxillary Expansion Signup and view all the answers

What is a frequent dental visit to monitor dental development, manage caries risk, and address any emerging issues promptly?

Regular Dental Check-Ups Signup and view all the answers

Study Notes

What is Achondroplasia?

A genetic disorder that affects the fibroblast growth factor receptor (FGFR3) protein, which regulates bone growth and maintenance.
The most common type of short stature skeletal dysplasia or dwarfism.

Genetic Mutations

Caused by specific pathogenic variants in FGFR3 on chromosome 4.
An autosomal dominant disorder, where one copy of the mutated gene is sufficient to cause the disorder.
80% of cases result from new (de novo) mutations, which occur spontaneously in the sperm or egg of one of the parents or during early embryonic development.

Pathogenesis

A specific mutation in the FGFR3 gene leads to an overactive receptor, inhibiting the proliferation and maturation of chondrocytes, which are responsible for cartilage formation.
This results in shortened and improperly formed bones, particularly affecting the long bones in the arms and legs.

Signs and Symptoms

Shortened bones (thigh, upper arm)
Short hands and feet
Large separation between third and fourth fingers
Head is larger than normal
Prominent forehead
Midface hypoplasia
Delayed development in infants (sitting, crawling, walking)
Foramen magnum stenosis

Diagnosis

Clinical Examination: Physical features such as large head size, prominent forehead, midface hypoplasia, short arms and legs, and short stature.
Radiographic Examination: X-rays reveal characteristic skeletal abnormalities, such as shortening of the long bones, a narrowed foramen magnum, and a small vertebral canal.
Genetic Testing: FGFR3 mutation testing can identify the mutations.

Treatment and Management

No specific treatment for achondroplasia, but managing symptoms and monitoring height, weight, and head circumference during infancy.
No cure for achondroplasia, but most people with the condition can live full and healthy lives.

Oral and Dental Manifestations

Midface hypoplasia: underdevelopment of the midface, resulting in a concave facial profile and a prominent lower jaw.
Dental crowding: reduced space in the upper jaw, leading to crowding of teeth.
Delayed dental development: slower eruption of primary and permanent teeth.
Malocclusion: misalignment of teeth, particularly Class III malocclusion (underbite).
Narrow dental arches: constricted upper and lower dental arches.
High-arched palate: elevated roof of the mouth, affecting speech and feeding.
Bite issues: problems with how the teeth come together, affecting chewing and speech.
Increased risk of dental caries and periodontal disease: higher risk of cavities and gum disease due to crowding and difficulty in maintaining oral hygiene.
Jaw growth and function problems: abnormal jaw growth patterns, leading to chewing difficulties and temporomandibular joint (TMJ) disorders.
Airway obstruction: narrowing of the airway due to facial structure anomalies, leading to obstructive sleep apnea.

Management Strategies

Interdisciplinary approach: collaboration between pediatric dentists, orthodontists, maxillofacial surgeons, and other healthcare providers.
Early orthodontic intervention: early assessment by an orthodontist to plan for space maintenance, expansion of dental arches, and correction of malocclusion.
Maxillary expansion: rapid maxillary expansion may be indicated to address the narrow maxilla and improve dental arch space.
Orthognathic surgery: in severe cases of malocclusion and maxillary hypoplasia, orthognathic surgery may be necessary to correct jaw alignment.
Regular dental check-ups: frequent dental visits to monitor dental development, manage caries risk, and address any emerging issues promptly.

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Description

Achondroplasia is a genetic disorder that affects the fibroblast growth factor receptor (FGFR3), impacting bone growth and brain development. Learn about this disorder and its effects on the body.