8. Single Gene Pathology 1 Flashcards
What is a single gene disorder
Pathogenic variant in a single gene = outdated model which suggests that a single variant in one gene causes one phenotype = not always true
What is allelic heterogeneity
Different pathogenic variants in a SINGLE gene —> MULTIPLE phenotypes
What is locus heterogeneity
Pathogenic variants in DIFFERENT genes —> ONE phenotype
What is achondroplasia and what are its symptoms
- short limb dwarfism
- bone abnormalities
- normal intelligence
What gene variant is achondroplasia caused by
Fibroblast growth factor receptor 3= FGFR3 (location = 4p16.3)
What is thanatophoric dysplasia and how does it present
A lethal embryonic condition
With severe bony abnormalities
Is thanatophoric dysplasia lethal
Yes
An abnormality is which gene causes thanotophoric dysplasia
FGFR3 = fibroblast growth factor receptor 3
What is Crouzon syndrome (with acanthosis nigircans)
Genetic disorder characterized by the premature fusion of certain skull bones (craniosynostosis). This early fusion prevents the skull from growing normally and affects the shape of the head and face.
Which genetic disorder is characterised by craniosynotosis
Crouzon syndrome
What is acanthosis Nigericans
A skin conditions around the eye
- present in Crouzon syndrome
Which gene abnormality can cause Crouzon syndrome
FGFR3
What is CATSHL syndrome and which gene abnormality is it caused by q
Camptodactyly
Tall stature
Hearing loss
Caused by abnormality in FGFR3
Give four conditions caused by abnormal FGFR3
Achondroplasia
Thanotophoric dysplasia
Crouzon syndrome with acnothosis Nigericans
CATSHL
How is FGFR3 an example of allelic heterogeneity
Pathogenic variants all in the same gene - FGFR3 - can cause such different phenotypes = eg, achondroplasia, CATSHL, Crouzon syndrome, thanotophoric dysplasia
