Genetics

Question 1

Alkaptonuria

Answer 1

Homogentisic acid oxidase deficiency leads to a defect in tyrosine metabolism and accumulation of homogentisic acid.
Rx is a dietary reduction of tyrosine and phenylalanine.

Question 2

Autosomal Dominant conditions

Answer 2

Achondroplasia
Ehlers Danlos syndrome
Familial adenomatous polyposis coli
Gilbert syndrome
Hereditary non-polyposis colorectal carcinoma
Huntington disease
Marian syndrome
Von Willebrand disease
Familial Hypercholesterolemia

Question 3

Autosomal Recessive conditions

Answer 3

Congenital adrenal hyperplasia
Cystic Fibrosis
Haemochromatosis
Wilsons disease
Sickle cell Anemia
Kartagener syndrome
Oculocutaneous albinism
Xeroderma pigmentosum

Question 4

X- Linked Recessive conditions

Answer 4

Becker Muscular dystrophy
Duchenne muscular dystrophy
Haemophilia A and B
Fabry’s disease
Hunter syndrome

Question 5

X- Linked Dominant conditions

Answer 5

Vitamin D-resistant rickets
Rett syndrome
Incontinentia pigmenti
Periventricular Nodular heterotopia

Question 6

Pseudoxanthoma Elasticum

Answer 6

• Autosomal recessive.
• Mutation in ABCC61 gene.
• Skin, eyes, and CVS, GIT
  SKIN
• yellow papules on the neck
• goosebumps, puckered, plucked chicken appearance
  EYES
  Angiod streaks
  yellow retinal mottling
  CVS
  Mitral valve prolapse/regurgitation
  Intermittent claudication
  GIT
  Bleeding from bowels
  Abdominal angina

Question 7

Kallmann Syndrome

Answer 7

Kallmann syndrome may arise due to abnormalities of the KAL-1 or KAL-2 gene (encoding anosmin-1 and FGF-1).

Whilst the majority of cases are sporadic, up to 50% of cases are due to genetic inheritance.

Kallmann presents with hypothalamic gonadotrophin-releasing hormone deficiency and deficient olfactory sense: hyposmia or anosmia.

FISH( Fluorescent in situ hybridisation) using a specific chromosomal probe, is currently the best means of a genetic diagnosis of this condition.

Question 8

Ehler- Danlos syndrome

Answer 8

Ehler-Danlos syndrome is an autosomal dominant connective tissue disorder that mostly affects type III collagen.

Features and complications
>elastic, fragile skin
>joint hypermobility: recurrent joint dislocation
>easy bruising
>aortic regurgitation, mitral valve prolapse and aortic dissection
>subarachnoid haemorrhage
>angioid retinal streaks