Monday 27 September 2010

MRCP revision battle 22.1: Goodpasture's Syndrome

Today's battles cover a lot of the random conditions that frequently appear as differentials in MRCP questions but rarely feature in your day-to-day life.  As well as being random, or possibly as a consequence of them being random, their exact causes are often unknown, their treatments are debated and they are just downright complex.  Can you tell from this opening gambit how much fun I've had preparing today's battles?!  Hopefully I've whittled them down to digestible forms and have tried to give links if I've whittled away too much.  I've also thrown in aortic regurgitation for some light relief... when aortic regurgitation is light relief you know its going to be a bad day....

So here goes, and good luck!!

MRCP revision battle 22.1: Goodpasture's Syndrome
MRCP revision battle 22.2: Neurofibromatosis
MRCP revision battle 22.3: Tuberous sclerosis
MRCP revision battle 22.4: Fanconi anaemia
MRCP revision battle 22.5: Fanconi syndrome
MRCP revision battle 22.6: Aortic regurgitation
MRCP revision battle 22.7: Argyll Robertson Pupil

MRCP revision battle 22.1: Goodpasture's Syndrome 

Goodpasture's syndrome is a rare condition caused by anti GBM antibodies and is characterised by pulmonary haemorrhage and renal failure.

There is less than 1 case per million people per year.
Cases may be triggered by inhaled hydrocarbons, paraquat or viral infections.

Pulmonary haemorrhage is treated by plasma exchange
Renal involvement is treated by steroids, cyclophosphamide and plasma exchange.

Renal biopsy would show:
  • IgG on basement membrane
  • crescent formation

For the really keen:

1 random battle down, several more to go...

MRCP revision battle 22.2: Neurofibromatosis

Neurofibromatosis is an autosomal dominant condition which causes lesions in the skin, nervous system and skeleton.

It is quite complex so below are just a few key points to learn for MRCP:

There are 2 types:

Neurofibromatosis 1 = von Recklinghausen's disease
  • chromosome 17, 1:2500
  • features include:
    • cafe au lait spots
    • axillary/inguinal freckling
    • lisch nodules in iris (seen in >90%)
    • perpheral neurofibromas
    • optic gliomas (2%)
    • osseous lesions
  • may have low IQ or renal artery stenosis

Neurofibromatosis 2
  • chromosome 22, rarer than NF 1
  • Features:
    • bilateral acoustic neuromas - sensorineural hearing loss is first sign
    • cafe au lait spots
    • juvenile posterior subcapsular lenticular opacity = a form of cataract

For the really keen:

So having got one complex, rare and unsatisfying battle out of the way lets jump straight into another...

MRCP revision battle 22.3: Tuberous sclerosis

This is going to be a very unsatisfying battle because tuberous sclerosis is rare and complex and essentially to grasp it properly goes far beyond what is required for MRCP, so please excuse my poor attempt at summarising some of the details which may be MRCP-relevant, particularly the skin manifestations...

Tuberous sclerosis is a rare, complex autosomal dominant condition which causes multiple benign tumours.

Features include:

  1. cutaneous features
    • ash leaf spots (appear under UV light)
    • shagreen patches
    • adenoma sebaceum
    • subungal fibromata
    • cafe au lait spots
  2. neurological features
    • epiplesy
    • low IQ
  3. other features
    • retinal haematoma
    • gliomas
    • renal cysts

For the really keen:

Now lets go on to the thankfully less complex topic of Fanconi anaemia...

MRCP revision battle 22.4: Fanconi anaemia

Fanconi anaemia is an autosomal recessive disorder which is characterised by:
  • pancytopenia secondary to bone marrow failure
  • dysmorphic features
    • short stature
    • microcephaly
    • absent radii
  • cafe au lait spots
  • susceptibility to cancers
    • AML
    • squamous cell cancers of head and neck
    • gynaecological  cancers

Most patients die by 30.

For the really keen:
emedicine article on Faconi anaemia 

For the rest of us lets move on to look at the similarly named, but completely different, Fanconi Syndrome

MRCP revision battle 22.5: Fanconi Syndrome

Fanconi syndrome is disturbance of proximal renal tubule function, resulting in defective reabsorption of:
  • amino acids
  • phosphate
  • potassium
  • glucose
  • bicarbonate

It can cause vitamin D resistant rickets.

Causes of Fanconi syndrome include:
  • idiopathic
  • inherited
    • cystinosis
    • Wilson's disease
  • acquired
    • heavy metal poisoning
    • light chains
      • amyloid
      • myloma

Treatment is:
  • treat cause
  • replace losses (potassium, bicarb, phosphate, vit D supplements)

Lets now move back mainstream with a revision battle with aortic regurgitation...

MRCP revision battle 22.6: Aortic regurgitation

Aortic regurgitation produces a fiendishly difficult to hear early diastolic murmur; I've heard it once and embarked on a most unprofessional victory dance once out of sight of the patient (even more embarrassingly it wasn't even me picking up the murmur, I had been sent to listen to the patient knowing they had the murmur...)

Possibly because its so hard to hear there are a whole troop of eponymous signs that can suggest aortic regurgitation, and MRCP exams love throwing them into questions to excite you:
  • Corrigan's sign: visible carotid pulsation 
  • de Mussets sign: the head bobs with each pulse
  • Duroziez's sign: femoral artery is compressed and auscultated proximally and a diastolic murmur is heard as blood flows backwards during diastole
  • Millers sign: pulsation of uvula
  • Quincke's sign: capillary pulsations in nail be
  • Traube's sign: pistol shot sound over femoral arteries

The less exciting but probably more important points to remember are:
  • the pulse is collapsing (=waterhammer)
  • wide pulse pressure
  • the apex is thrusting

As well as the classic early diastolic murmur best heard down the left sternal edge which is loudest when the patient is leaning forward and in expiration, you need to be aware of the Austin Flint murmur.

Austin Flint murmur only occurs in severe aortic incompetence.  It is a mid diastolic murmur and is probably due to the regurgitant jet interfering with the opening of the mitral valve.

Symptoms of AR are:
  • dyspnoea
  • palpitations
  • heart failure

Causes of AR include:
  • valve inflammation
    • rheumatic fever
    • IE
    • RA
    • SLE
    • appetite supressants
  • aortic root disease
    • hypertension
    • syphillis
    • aortic dissection
    • ankylosing spondylitis
    • psoriasis
  • collagen diseases
    • hurlers syndrome
    • marfans
    • psuedoxanthoma elasticum
One way to remember these causes is SIR AA SHARP  plus collagen.

Management: the aim is to replace the valve before significant LV dysfunction.  Indications for surgery are increasing symptoms, enlarging heart (CXR/echo), worsening ECG (TWI laterally)

Onwards to the brief final battle - the Argyll Robertson Pupil

MRCP revision battle 22.7: Argyll Robertson Pupil

I love the Argyll Robertson pupil, and have done ever since a very serious elderly consultant intoned to us that "the Argyll Robertson pupil is like a prostitute... it will accommodate but will not react."

Essentially the Argyll Roberston pupil is a pupil that:
  • will not react to light
  • will accommodate

It is a sign of neurosyphillis, but a similar phenomenon occurs in diabetes.
They are also seen in Parinaud's syndrome, which will be covered tomorrow.

And on that teaser, adieu!