Craniofacial Pathologies Flashcards
What is ectodermal dysplasia?
A group of closely related conditions caused by a defect in the ectoderm, leading to defective hair, nails, sweat glands, skin and teeth
What is the typical way that all ectoderm tissues form?
All form from a sheet of epithelium sitting flat on top of mesenchyme.
Then get formation of a placode which is where the epithelium proliferates in a specific place.
The placode extends into the surrounding mesenchyme to create a bud.
What are the 4 inheritance types of ectodermal dysplasia?
- Autosomal dominant
- Autosomal recessive
- X-linked dominant
- X-linked recessive
What type of ectodermal dysplasia is most common?
What are the 3 main symptoms?
Hypohidrotic ectodermal dysplasia (affecting sweat glands)
- Missing or sparse hair
- Missing or misshapen teeth (peg shaped, failure of roots to bifurcate)
- Absent or reduced sweating
Why are missing sweat glands an issue?
Problems in temperature regulation.
Big problem in babies.
Leads to dry skin and eczema.
Why are missing respiratory glands an issue?
Reduction in mucosa in trachea.
Failure to clear respiratory tract of debris
High incidence of respiratory infections
Why are missing salivary glands an issue?
Increased risk of caries and candida infections.
What pathway causes ectodermal dysplasia?
Mutation in the ectodysplasin pathway (Eda).
- tends to be mutation on the gene itself or mutation on the gene receptor
Are females or males more likely to get this?
Majority of cases are X linked.
More males affected, females more likely to be carriers.
How does the Eda signalling pathway work?
EDA PROTEIN forms a trimer.
Ligand binds to the eda receptor on the cell membrane.
On binding, we recruitment of intracellular protein that creates a complex and sends a signal inside the cell.
Where do we find Eda and Edar in a developing tooth?
Eda being expressed around the epithelium of the tooth.
Edar - receptor for eda in the middle of the epithelium of the tooth in the enamel knot
In all = Eda around the epithelium and Edar in the epithelium.
Why do we get defects in developing tooth roots?
Edar expression in the hertwigs epithelial root sheath.
What happens to salivary glands in ectodermal dysplasia?
Get reduced branching
How can we rescue the X - linked Eda?
Eda gene is the ligand. Missing this ligand so can try and put the missing ligand back in during pre and post natal development.
What did inserting Eda into mice do?
It recovers hair, tooth cusps, eyelid glands, sweat glands.
