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Health Science > Hereditary Haemochromatosis > Flashcards

Hereditary Haemochromatosis Flashcards

Caoimhe

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1
Q

Haem sources of iron

A

animal meat

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2
Q

non haem sources of iron

A

lentils, beans, leafy veg and fortified cereals

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3
Q

What does an iron deficiency often result from

A
  • Insufficient consumption
  • Malabsorption (e.g: coeliac)
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4
Q

Where is iron absorbed

A

In the duodenum

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5
Q

What carrier protein is iron linked to in the blood

A

Transferrin

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6
Q

How does haem bind to transferrin

A

Old erythrocytes are broken down by macrophages in the liver and spleen and released haem binds to transferrin

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7
Q

Where is ferritin synthesised and stored

A

Ferritin is synthesised in the liver and stored in the liver, spleen, skeletal muscles and bone marrow

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7
Q

What is ferritin

A

A water soluble iron storage protein

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8
Q

What is Haemosiderin

A

Haemosiderin is a water insoluble iron storage complex

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9
Q

Where is haemosiderin found

A

Haemosiderin is found in macrophages

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10
Q

Ways that iron is excreted from the body

A
  • Bile
  • Faeces
  • Urine
  • Menstruation
  • Intestinal exfoliation
  • Skin desquamation
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11
Q

When is iron recycling critical

A

Iron recycling is critical when dietary iron is often 10x less than that recquired daily (20 mg)

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12
Q

What happens when iron concentration is increased

A
  • Increased ferritin concentration
  • HFE (human homeostatic iron regulator protein) upregulates hepcidin via signalling pathway, where hepcidin decreases iron levels by reducing dietary absorption
  • Hepcidin downregulates ferroportin, where ferroportin is a transmembrane protein that transports Fe from inside the cell to outside the cell (intracellular to blood)
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13
Q

What is HH characterised by

A

Chronic excessive intestinal absorption of dietary iron and a pathological increase in iron stores within the body

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14
Q

Where does the excess iron accumulate

A

In tissues and organs such as the liver, pancreas, heart, joints, skin, gonads, thyroid, pituitary gland etc..

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15
Q

Symptoms of HH (8)

A
  1. Fatigue
  2. Joint pain
  3. Abdominal pain
  4. Skin discolouration (grey or bronze)
  5. Arrythmia
  6. Erectile dysfunction / decreased libido
  7. Symptoms of endocrine impairment
16
Q

Which HH types are autosomal recessive (AR)

A

Types 1-3

17
Q

What type of HH is autosomal dominant (AD) and what is this type known as

A

Type 4 is autosomal dominant. It is also called ferroportin disease

17
Q

What causes Type 1 HH? (2)

A
  1. A cysteine to tyrosine substitution at amino acid 282 (C282Y)
  2. An aspartate to histidine substitution at amino acid 63 (H63D) on the HFE gene encoding the HFE protein
18
Q

What is type 2 HH called

A

Juvenile Haemochromatosis (JH)

19
Q

What is type 2 HH caused by

A

JH is caused by mutations in the HJV gene that encode an iron regulatory protein haemojuvelin

20
Q

What is type 3 HH caused by

A

Mutations in the TfR2 gene that codes for the transferrin receptor protein TfR2
Note: Tfr2 mediates cellular uptake of transferrin bound iron and is involved in iron metabolism

21
Q

What causes type 4 HH

A

Ferroportin disease is caused by mutations in the SLC40A1 gene that codes for ferroportin
Note: ferroportin is a transmembrane protein that transports iron from cell to blood

22
Q

Type 1 HH pathogenesis

A
  • Mutated HFE results in increased conc of iron (HFE normally functions to decrease iron concentrations by upregulating hepcidin. Hepcidin decreases iron conc by reducing dietary absorption)
  • Hepcidin deficiency, iron absorption not reduced in response to high levels
  • Ferroportin not downregulated (due to Hepcidin deficiency) and iron continues to be exported to blood
  • Increased ferritin
  • Transferrin saturation
23
Q

Type 2 HH pathogenesis

A
  • Haemojuvelin regulates hepcidin
  • Mutated HJV = dysregulated hepcidin and inability to reduce serum iron concentrations
  • Hepcidin deficiency
24
Q

Type 3 HH pathogenesis

A
  • Transferrin receptor protein 2 (TfR2) mediates cellular update of transferrin bound iron
  • Mutated TfR2 = TfR2 deficiency and inability to reduce serum iron concentrations
25
Q

Type 4 HH pathogenesis

A
  • Ferroportin = a transmembrane protein that transports iron from inside cell to outside cell
  • Mutated SLC40A1 = excessive cellular iron and consequent tissue damage
    Note: Iron toxic in high concentrations
26
Q

HH complications (8)

A
  1. Splenic and liver iron overload and consequent dysfunction -> some develop hepatic fibrosis and cirrhosis, risk factors for HCC
  2. DM -> due to pancreatic iron deposition
  3. Arrythmia and congestive heart failure -> iron deposition in muscle fibres and conductivity system
  4. Hypogonadism/amenorrhoea -> due to iron induced hypothalamic/pituitary/endocrine dysfunction
  5. Skin hyperpigmentation -> due to increased synthesis of melanin
  6. Osteoporosis -> due to excess iron disturing the balance between bone resorption and formation
  7. Increased risk of infection foodborne bacteria -> e.g: Listeria monocytogenes requires iron for growth
  8. Anaemia -> impaired iron export and iron sequestration (liver and spleen overload)
27
Q

When do symptoms of types 1-3 manifest

A

Adulthood

28
Q

What age does JH usually become apparent

A

10-30 years

29
Q

What is the most common treatment for management of HH

A

Phlebotomy

30
Q

2 stages of phlebotomy tx

A
  1. Induction: blood removed frequently until serum iron levels are normal (can take 12 months)
  2. Maintenance: blood removed less often (quarterly/biannually) to manage iron levels
31
Q

What tx used when phlebotomy is not possible

A

Chelation therapy

32
Q

How does chelation therapy work

A

Chelating agent binds to iron and is excreted via faeces or urine

33
Q

Side effects of chelation therapy

A
  1. GI symptoms
  2. Dizziness
  3. Visual or auditory impairments
  4. Muscle cramps
  5. Tachycardia (fast heart rate)
  6. Thrombocytopenia
34
Q

How does the HH tx Therapeutic Erythrocytaphersis work

A

It’s the removal of erythrocytes rather than whole blood

35
Q

HH tx: Diet

A
  • Avoidance of foods fortified with iron
  • Avoidance of alcohol -> as it affects hepsulin, avoid ARLD
  • Avoid raw bivalves (oysters/clams)

Health Science (10 decks)

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