Genetics Flashcards
1
Q
What is the presentation colorectal cancer?
A
- Anaemia
- Change in bowel habit
- PR bleeding
- Tenesmus
- Obstruction
2
Q
What hereditary factors are there for colorectal cancer?
A
- Autosomal dominant = Lynch syndrome
- Autosoma recessive = Familial presentations/ polygenic inheritance
3
Q
Summarise cancer genetics
A
Activation of oncogenes + silencing of tumour suppressors
4
Q
How many mutations are required to inactivate tumour suppressor genes?
A
2 mutations
5
Q
How to oncogenes arise?
A
1 mutation
Proto-oncogenes > oncogenes
e.g. KRAS
6
Q
What advantage do cancerous gene mutations lead to?
A
- Growth independently
- Insensitive to growth inhibitory signals
- Evasion of apoptosis
- Create own vascular supply
- Tissue invasion/metastasis
- Immune evasion
7
Q
What is FAP?
A
- Familial adenomatous polyposis
- Autosomal dominant
- Thousands of polyps throughout large bowel
- Due to mutation in APC on chromosome 5
- All develop CRC
8
Q
What are the extra intestinal manifestations of FAP?
A
Cancers
- Thyroid
- Brain (medulloblastoma)
- Hepatoblastoma
- Heptabiliary tree
- Adrenal
Benign lesions
- CHRPE = Congenital hypertrophy of the retinal pigment epithelium
- Epidermoid cysts
- Osteomas
- Desmoid tumours
- Supernumerary teeth
- Adrenal glans adenomas
9
Q
How is FAP treated?
A
Colecotomy
- ileorectal anastomosis
- ileal pouch
- stoma
10
Q
What is Lynch syndrome?
A
- Most common inherited predisposition to colorectal cancer
- Defects in mismatch repair genes - MLH1, MHS2, MSH6, PMS2 = early onset cancers
