Genetics Flashcards
What are the 6 different forms of monogenic inheritance?
Autosomal dominant
Autosomal recessive
Mitochondrial
X-linked dominant
X-linked recessive
Y-linked
How many genes are involved in a mendelian disorder?
Only 1 - hence MONOgenic.
What is consanguinity?
When a mother and father are related.
This conveys an increased risk of autosomal recessive inheritance.
What are Y-linked disorders fairly rare?
They commonly cause infertility - thus, are not passed on.
How can a mitochondrial disease be identified?
Mother will be affected, along with ALL of their children.
What are the 3 cancer ‘P’s of MEN1 syndrome?
Pituitary
Pancreas
Parathyroid
What form of inheritance is observed in MEN1?
Autosomal dominant
Most affected will die due to this condition - often because of malignant pancreatic neuroendocrine tumors.
Who should be tested for MEN1?
Those suffering from 2 or more MEN1-associated tumors
Those that have developed neuroendocrine tumors at a young age
Those with an affected relative
What form of inheritance is seen in MEN2?
Autosomal dominant
Affects the RET gene
What is the most common form of MEN2 synrome?
MEN2A
What are the characteristic features of MEN2A?
Medullary thyroid carcinoma
Phaeochromocytoma
Parathyroid tumors
What are the characteristic features of MEN2B?
Medullary thyroid carcinoma
Phaeochromocytoma
Marfanoid habitus
Mucosal neuromas
What is the primary cause of death in MEN2?
Medullary thyroid carcinoma
How is MTC diagnosed?
USS and FNA
Calcitonin levels (acts as a tumor marker as it is produced by C-cells)
How is phaeochromocytoma diagnosed?
Elevated urinary/plasma metanephrines
What characterises Von-Hippel Lindau syndrome?
Retinal and CNS hemangiomas/hemangioblastomas
Significant risk is also associated with developing clear cell renal carcinoma in these patients.
How is Klinefelter’s Syndrome diagnosed?
Karyotyping - look for an additional sex chromosome.
How does Klinefelter’s Syndrome present?
Will appear more feminine.
They will be infertile, with small, firm testes.
Increased risk of cryptorchidism, learning difficulties and breast cancer.
Aside from genetic causation, what other causes exist for primary hypogonadism?
Medications
Infiltrative disease (e.g. haemochromatosis)
Chemotherapy
Testicular trauma
What genetic disorder produces secondary hypogonadism?
Kallmann’s Syndrome
How does Kallmann’s Syndrome present?
Isolated GnRH deficiency and hyposmia/anosmia
One kidney only
Red/Green colour blindness
Cleft lip
Is Kallmann’s Syndrome or Klinefelter’s Syndrome rarer?
Kallmann’s is less prevalent.
What are causes of secondary hypogonadism?
Kallmann’s Syndrome
Prader-Willi Syndrome
Damage to the pituitary
Obesity
Medications
Acute illness
Eating disorder
How should a male complaining of infertility be investigated?
Semen analysis
At what time of day should testosterone be measured?
Between 8am and 11am.
In what individuals is testosterone therapy contraindicated?
Hormone responsive cancer/ prostate cancer diagnosis
Haematocrit >50%
Severe sleep apnoea/heart failure
