Friday 24 September 2010

MRCP revision battle 19.1: Myelofibrosis

I have more time than usual to revise this week and am actually finding it harder to sit down and get on with it... must have a quiet word with the motivational centres of my brain (which I believe are the mesolimbic areas... anyone care to correct me?)  Anyway, today's battles will be:

MRCP revision battle 19.1: Myelofibrosis
MRCP revision battle 19.2: Hepatitis
MRCP revision battle 19.3: Peutz Jegher Syndrome
MRCP revision battle 19.4: Familial Adenomatous Polyposis
MRCP revision battle 19.5: Hereditary Non-Polyposis Colorectal Cancer
MRCP revision battle 19.6: LTOT
MRCP revision battle 19.7: Exercise tolerance tests
MRCP revision battle 19.8: Lead poisoning

MRCP revision battle 19.1: Myelofibrosis

Myelofibrosis has always been a secret 'sweet-spot' of mine - I think because of its 'teardrop cells' - so its a good battle to start this unmotivated day on...

Myelofibrosis is fundamentally fibrosis of the bone marrow.  There is hyperplasia of megakaryocytes which produce platelet-derived growth factor, leading to:
  1. marrow fibrosis
  2. haemopoesis being forced to move to the spleen and liver.

Features of myelofibrosis include:
  • lethargy
  • weight loss
  • night sweats
  • massive hepato/splenomegaly

Investigations show:
  • raised WCC, low Hb
  • teardrop pokilocytes
  • leucoerythroblastic cells (=nucleated red cells)
  • raised LDH and urate as increased cell turnover
  • bone marrow may produced a 'dry tap'

Image below shows teardrop cells.

    Treatment is ?allogenic stem cell transplant.

    Prognosis is poor with a median survival of 4 to 5 yrs.

    Onwards to hepatitis.... 

    MRCP revision battle 19.2: Hepatitis

    There are 5 'flavours' of viral hepatitis, labeled A to E.  Important general points to learn are:
    • all are caused by RNA virus' except hepatitis B, which is a DNA virus
    • B and C are spread by blood/sexual contact
    • A and E are spread by the faecal-oral route
    • Hepatitis D essentially is only ever found as a co-infection, never alone.

    So to explore the 3 most popular MRCP 'flavours' in more depth....

    Hepatitis A:
    • spread faeco-orally, so look out for questions featuring backpackers returning home
    • incubation period is 2-6 weeks
    • presents as fever, malaise, nausea
    • patient likely to be jaundiced and may have hepato/splenomegaly
    • treatment is supportive
    • patients generally make a full recovery

    Hepatitis B:
    • symptoms are similar to hep A
    • incubation period is longer at 1 - 6 months
    • spread is blood/bodily fluids - questions likely to hint at male business traveller or other innuendo
    • important to fully grasp the various antigens and their meanings:
      • HBsAg: present for 1-6 months after exposure; if present for >6 months patient is a carrier
      • HBeAg: present for 1.5-3 months after exposure and is marker of high infectivity
      • anti HBC IgM - signifies acute infection/carrier
      • anti HBC IgG - may be acute infection, carrier or cleared infection
      • anti HBS - if present with anti HBC suggests recovered from hep B and naturally immune; if present alone suggests hep B vaccination
    • complications of hepatitis B include:
      • 5-10% chronic hepatitis
      • glomerulonephritis
      • increased risk hepatocellular carcinoma
      • cryoglobulinaemia

    Hepatitis C:
    • is spread by blood/sexual contact
    • blood pre 1991 wasn't screened for hep C
    • <20% get an acute hepatitis but 80% get chronic hepatitis
    • breast feeding is NOT contraindicated (a common MRCP fascination for some reason)
    • complications:
      • 80% chronic hepatitis
      • 20% cirrhosis
      • increased risk hepatocellular carcinoma
    • Treatment: IFN alpha and ribavirin

    After that wizz through some high-yield viral hepatitis facts lets move on to Peutz Jegher Syndrome

    MRCP revision battle 19.3: Peutz Jegher Syndrome

    Peutz Jegher Syndrome is a condition characterised by:
    • pigmented 'freckles' (macules) on lips, face, palms and soles
    • hamartomatous polyps in gastrointestinal tract

    It is an autosomal dominant condition caused by a mutation of gene LKB1

    Complications of PJS include:
    • obstruction/intususception
    • GI haemorrhage
    • iron deficiency
    • colicky abdo pain
    • malignant transformation - around 50% of sufferers will have died from a cancer by the age of 60.

    There is no specific treatment.

    So lets move on from a relatively benign cause of multiple colonic polyps to a less benign one....

    MRCP revision battle 19.4: Familial Adenomatous Polyposis

    Familial adenomatous polyposis is an inherited condition in which patients develop literally thousands of polyps in the GI tract.  Virtually all sufferers will get cancer, usually in their 30s or 40s.

    It is caused by a mutation in the tumour supressor gene APC on chromosome 5.

    The appearance of the colon is:

    Treatment tends to be a colectomy before cancer develops.

    As an aside, a variation of FAP called 'Gardners Syndrome' exists.  This is FAP plus osteomas, epidermal cysts, fibromas and retinal pigmentation.

    So after 2 conditions which are defined by polyps, lets look at one which defines itself by not having polyps - Hereditary Non-Polyposis Colorectal Cancer

    MRCP revision battle 19.5: Hereditary Non-Polyposis Colorectal Cancer

    Hereditary Non-Polyposis Colorectal Cancer is an autosomal dominant condition associated with an increased risk of colorectal cancer.

    90% of patients with HNPCC develop cancers, usually in the proximal colon and often poorly differentiated/highly aggressive cancers.

    There is also an increased risk of breast, ovary and endometrial cancers.

    HNPCC is defined by the Amsterdam criteria:
    • at least 3 family members with colon cancer (one a 1st degree relative)
    • at least 2 generations affected
    • at least 1 diagnosed under 50 yrs of age

    Thats quite enough bowels for one day, lets come up for some oxygen...

    MRCP revision battle 19.6: LTOT

    LTOT = long term oxygen therapy = 15 or more hours of oxygen per day.

    This is the only treatment to increase survival in COPD.

    NICE recommends it if:
    • PaO2 <7.3kPa OR
    • PaO2 <8kPa if
      • secondary polycythaemia
      • nocturnal hypoxia (questions may note 'morning headaches;
      • peripheral oedema
      • pulmonary hypertension

    How about now trying our exercise tolerance...

    MRCP revision battle 19.7: Exercise tolerance tests

    Exercise tolerance tests are starting to go out of fashion but are still currently a mainstay of assessment of angina. 

    I'd recommend this BMJ article for a comprehensive discussion; what follows below are just a few salient MRCP points.

    ETTs are carried out according to the Bruce protocol, which is 7 sections each 3 minutes long so a maximum of 21 minutes of exercise.  A modified bruce can be used in higher risk/frailer patients.

    Beta blockers must be stopped the day before an ETT
    Digoxin should be stopped a week before.

    The test is deemed to be positive if:
    • anginal symptoms
    • BP decreases by 15mmHg or fails to increase on exercise
    • arrhythmia
    • ST depression
    • failure to achieve target heartrate (220-age in men, 210-age in women)
    • ST elevation

    Now for the last battle of the day, lead poisoning

    MRCP revision battle 19.8: Lead poisoning

    Lead poisoning is a good topic as it has 2 nice distinctive features (blue lines on nail growth margins and basophillic stippling of red blood cells.)

    A more comprehensive list of lead poisoning features is:
    • abdominal pain
    • constipation
    • peripheral neuropathy
    • fatigue

    Blue lines on the growth margin of nails affect 20% adults with lead poisoning but are rare in children.

    Investigations should show:
    • microcytic anaemia
    • basophillic stippling of red blood cells
    • raised aminolevulinic acid levels (a haem precursor)

     The image below shows basophillic stippling of red blood cells (right and left arrows)

    Treatment is by chelation with either EDTA, d-penicillamine or dimercaprol.

    Thats today wrapped up; questions on yesterday's battles can be found here

    MRCP questions: War 18

    As with previous 'wars' after 'battles' these are just a few quick questions to see if your brain cells have retained the information provided in battles 18.1 to 18.8.

    Grab a piece of paper, jot down your answers then compare them to my answers here

    Question 1:
    Which 4 clotting cascade factors is vitamin K a cofactor for?

    Question 2:
    Your patient has an INR of 7 but no evidence of bleeding.  What would you do?

    Question 3:
    A 20 year old comes to you with a rash across their back of teardrop-shaped lesions topped with some silver scales.  They note they had a sore throat a week or 2 ago.  What is the rash?

    Question 4:
    State the classical triad of symptoms for aortic stenosis.

    Question 5:
    A patient tells you their cardiologist said the pressure gradient across their aortic valve was 52mmHg.  What grade of severity is their stenosis?

    Question 6:
    Your houseofficer has diagnosed PMR and wants to know how to treat it.  What would you prescribe?

    Question 7:
    A mum brings her 16 year old son who has learning difficulties to you, saying he has been itching his bottom a lot recently.  You think he has threadworms.  How would you treat them?

    Question 8:
    Your consultant states he is admitting someone with pseudopseudohypoparathyroidism.  What blood results would you expect?

    The answers are here