CM- Genes, Cancer and the Liver Flashcards
Describe how iron is absorbed from the diet.
Hepcidin (a protein synthesized in the liver) controls the level of iron absorption from the diet through intestinal epithelial cells by blocking ferroportin on the basolateral membrane (thus not letting iron into the blood)
In iron overload states, how does excess iron enter the body?
- the normal pathway (through epithelial cells in the intestine)
- classic hemochromatosis where too much is absorbed
- more iron in the diet/medication - Parenterally in blood transfusions (congenital and acquired anemia)
What 4 factors regulate hepcidin synthesis?
- iron stores (high iron, increase hepcidin)
- anemia (you need more iron so decrease H)
- erythropoietic rate (higher rate= less H)
- hypoxia (suppresses H)
Describe the path of iron when it get into the blood.
- binds to circulating plasma transferrin which delivers it to cells
- cells make heme or cellular enzymes
- excess is stored as ferritin
What is the most common genetic mutation associated with iron overload?
Describe the mutation.
In Celtics– classic hereditary hemochromatosis (type 1)
It is a mutation in an HLA-like molecule that results in increased iron absorption despite iron overload.
It is a failure of ferroportin to be regulated by hepcidin
How do blood transfusions cause iron overload?
- there is no for normal pathway for the body to get rid of excess iron when it reaches the blood (regulation occurs at the level of the intestines)
- underlying anemia my down-regulate hepcidin, thus allowing more iron to be absorbed from diet
You get lab tests back that are: Iron: low TIBC: high Saturation: low Transferrin receptor: high Ferritin: low
What is the problem? What is the net effect in normal people?
This person has an iron deficiency. In normal individuals, hepcidin will decrease allowing ferroportin to take more iron in from the diet.
- increase iron absorption
- increase cell iron uptake
You get lab tests back that are: Iron: high TIBC: low Saturation: high Transferrin receptors: low Ferritin: high
What is the problem? What is the net effect for normal people?
This person is iron overloaded. They need to upregulate hepcidin to:
- decrease absorption from the intestines
- decrease cell iron uptake
In what organs does iron accumulate? What is the negative sequelae associated with each organ? (6)
- Liver- cirrhosis
- Heart- cardiomyopathy
- pancreas- DM
- testes- hypogonadism
- joints- calcium pyrophosphate crystal arthropathy (pseudogout)
- skin- pigmentation (bronze skin)
Why is the liver disproportionately affected in iron overload from a dietary source?
because there is a first pass effect of dietary iron in portal blood.
When iron stores are saturated (ferritin), iron-mediated fibrosis develops.
What is the threshold for hepatic iron to demonstrate fibrosis/cirrhosis?
What happens to the threshold if there is concurrent viral/alcohol factors?
Between 20-30 mg/g dry weight hepatic iron is the threshold for fibrosis/cirrhosis
If there is alcohol or viral factors, the threshold drops to 10-20mg/g dry weight
How do most patients today present with iron overload?
Patients are likely to be asymptomatic with non-specific fatigue or arthralgia. They will have elevated Fe #s on standard testing.
What tests are used to assess iron overload?
Routine liver tests will vary with the stage of disease so you need to rely on:
- transferrin, ferritin
- genetic tests for hereditary hemochromatosis
- non-invasive radiologic studies can suggest Fe but are not quantitative
- biopsy if LFTs or enzymes are abnormal to stage the fibrosis
- phlebotomy to get rid of excess Fe
What will the serum iron level be in:
- Fe Overload
- Inflammation
- Iron deficiency
- high
- low-normal
- low
What will the TIBC be for:
- Fe overload
- inflammation
- Fe deficiency
- low
- low
- high
What will Fe saturation be for:
- Fe overload
- inflammation
- Fe deficiency
- high
- high
- low
What will ferritin levels be for:
- Fe overload
- inflammation
- Fe deficiency
- normal early and high late
- high
- low
What will the hepcidin levels be for:
- Fe overload
- inflammation
- Fe deficiency
- low
- high
- low
What specific mutation accounts for the majority of patients with classic hereditary hemochromatosis?
What genetic test is available to confirm this?
Cys282Tyr - homozygous
Genetic test is for HFE
What is the difference between hemochromatosis and hemosiderosis?
Hemochromatosis = genetic iron overload
- cys282tyr homozygous or His63Asp heterozygous which interact with transferring receptor 1
Hemosiderosis = secondary iron overload
- transfusion
- hyperabsorption in response to anemia, hypoxia
- meds or diet
- advanced liver disease
What is the simplest way to manage excess iron? When is this challenging?
phlebotomy- this can be challenging if there is an underlying anemia.
It decreases serum ferritin to almost 0 by 8 months
Transferrin saturation drops at the 8 month mark
How is copper absorbed into the body?
It is absorbed from the diet. Normal is 1-5mg/day.
In intestinal epithelial cells it is either:
- bound to metallothioneins
- transported into the blood (25-60%)
What happens to copper when it reaches the blood?
It is bound to albumin and transported to hepatocytes where it is taken up.
A very little bit of copper can escape hepatic uptake and is excrete in urine (<40microns/day)
What happens to copper in the hepatocyte?
It is attached to chaperone proteins and transporters that:
- prevent toxicity
- facilitate incorporation into ceruloplasmin
- facilitate excretion into the bile
Where is ceruloplasmin synthesized? How many copper atoms can be incorporated in it?
What happens to ceruloplasmin levels with inflammation?
What happens to ceruloplasmin with copper overload?
It is synthesized in the liver and 6-7 copper atoms can incorporate.
It accounts for the majority of serum copper.
Inflammation: increase
Copper overload : decrease ( also with protein losing states and advanced liver disease)
What happens to cells when there is copper overload?
- deleterious oxidation of lipids and proteins
2. free radical formation
What is the defect in Wilson’s disease?
There is an intra-cellular copper transporter defect so copper is not incorporated into ceruloplasmin OR excreted into bile.
The copper just builds in hepatocytes, oxidizing fat and protein and creating free radicals. This leads to cell damage and chronic cirrhosis. When excess copper is released to blood, it damages RBCs increasing bilirubin and leading to more liver problems
In addition to Wilson’s disease, in what other two situations is copper excretion impaired?
- PBC
2. PSC
How do patients present with Wilson’s disease?
What age, what clinical presentation?
- hepatic illness- can be abrupt or insidious
- hemolytic anemia (DAT negative)
- cirrhosis
- under age 5 or OVER age 40
(5-10 years later)
- neuropsychiatric illness
- deposition in the basal ganglia and cerebellum
- parkinsons, dystonia, chorea, MS
- Corneal Kayser-Fleischer rings
What is used in the investigation to see if it is Wilson’s disease?
Measurements of :
- ceruloplasmin (low)
- liver copper (high) - definitive diagnosis
- urinary copper (high) - most cost-effective way to screen
What could manipulate ceruloplasmin tests to give a false positive for Wilson’s?
False negative?
FP:
- low protein disorders
- heterozygotes for wilsons
FN Inflammation (because it raises ceruloplasmin)
What could manipulate Cu urine to give a false positive for Wilsons? False negative?
FP
1. cholestasis (Cu in bile, but bile not excreted)
FN
1. incomplete collection
What could manipulate hepatic copper to give a false positive for Wilson’s? False negative?
FP
1. Cholestasis
FN
1. sampling or technical error
Why are genetic studies for Wilson’s disease ineffective?
There are many different mutations.
This is overcome by identifying common markers on the long arm of chromosome 13
What is the DDx for Wilson’s disease?
- fulminant liver disease (chronic with acute decompensation)
- cirrhosis - autoimmune 1st because it occurs in children
- neuropsychiatric disorders
- low ceruloplasmin from low protein disorder or heterozygous Wilson’s
- elevated hepatic copper from:
- chronic cholestasis (PBC, PSC)
- Indian childhood cirrhosis
How is Cu overload managed and treated?
D-penacillamine which is a copper chelator. It binds it and removes the excess copper
If someone presents with really low haptoglobin what does that mean? What disease should you be considering?
Low haptoglobin means there is hemolysis occuring.
This means you should consider Wilson’s disease because the excess copper hemolyzes RBCs.
What are the 5 main risk factors for developing hepatocellular carcinoma?
- Hep B- even without cirrhosis
- Hep C - always with cirrhosis
- Cirrhotic liver disease
- hemochromatosis
- autoimmune
- alcoholic liver disease - Carcinogens
- aflatoxin
- oral contraceptives, androgens
- tobacco - hereditary tyrosinemia
How is Hep B able to cause hepatocellular carcinoma without cirrhosis?
- effects of X gene product that activates intracellular signalling cascades
- insertion of viral genome with resulting critical mutation
When will patients typically present with pain from hepatocellular carcinoma?
It will cause pain when the liver capsule is stretched and if it touches the diaphragm pain will radiate to the right shoulder.
A patient experiences early satiety and has chronic liver disease. What are you suspicious of?
HCC- large left lobe compressing the stomach
You are screening a patient and find increased alpha fetoprotein. They are jaundiced and have ascites. What are you concerned about?
HCC
What is the mainstay for diagnosis of HCC?
quadruple phase CT (non-contrast, portal venous, arterial contrast, delayed contrast)
This is more expensive than ultrasound, but also more specific.
You are looking at a patients CT and there is a hypervascular lesion >2cm with unexplained a-fetoprotein >200ng/ml. What is the diagnosis assumed to be?
HCC
What is the DDX for HCC if there are abnormal liver tests, and symptoms OTHER than isolated abdominal pain?
- benign regenerating nodule in cirrhosis
- mets
- cholangiocarcinoma
- adenoma
What is the DDx for HCC if there is normal liver tests and abdominal pain?
- hemangioma
- cysts
- focal nodular hyperplasia
- adenoma
What is the DDx for elevated a-fetoprotein?
- HCC
- testicular cancer
- regenerating liver
How do physicians decide whether to do surgery for HCC removing the cancerous lesion while leaving enough liver to regenerate?
Each patient is considered by a doctor in:
- hepatology
- hepatobililary surgery
- interventional radiology
- oncology
If the person has advanced liver disease surgery is not possible. They need a transplant
What non-curative therapies are considered for HCC?
Destruction of neoplastic tissue while preserving as much function as possible.
- radiofrequency ablation
- chemoembolization
These decrease symptoms and slow progression
What is palliative treatment for HCC?
Narcotic analgesic regimens to treat pain
What 3 pieces of data are used in the Model of End-stage Liver Disease (MELD) determination of who get liver transplants?
- bilirubin
- INR
- creatinine
(function tests NOT hepatic damage tests)
When does the benefits of transplantation outweigh the risks of surgery?
MELD >16
