Saturday 20 November 2010

MRCP revision battle 55.1: Trypanosomiasis

More randomness...


MRCP revision battle 55.1: Trypanosomiasis
MRCP revision battle 55.2: Hypokalaemia
MRCP revision battle 55.3: Cryoglobulins
MRCP revision battle 55.4: Cold agglutinins
MRCP revision battle 55.5: Lateral medullary syndrome
MRCP revision battle 55.6: Purtscher retinopathy
MRCP revision battle 55.7: Optic atrophy




MRCP revision battle 55.1: Trypanosomiasis

Trypanosomiasis = diseases causes by parasitic protozoa trypanosoma.


2 main divisions:



1. African = sleeping sickness
  • spread by tsetse fly
  •  caused by
    • t. rhodesiense - east africa - quicker
    • t.gambiense - west africa - slower
  • classical presentation 
    • fever, rigors, headache, hepatosplenomegaly, lymphadenopathy
    • sleepy during day, awake at night
    •  meningoencephalitis
  • look for chancre and posterior cervical nodes (=Winterbottom's sign)
  • diagnosis is by microscopy
  • treatment:
    • IV pentamide
    • IV melarsoprol
Below is an image of t.gambiense:



2. American - Chagas disease
  • carried by triatomine bugs
  • caused by t. cruzi
  • classical presentation
    • fever, rash, hepatosplenomegaly, lymphadenopathy 
    • myocarditis
    • meningoencephalitis
    • megaoesophagus/megacolon
  • look for:
    • chagoma (=indurated, erythamatous nodule at site of infection)
    • periorbital oedema (=Romana's sign)
  •  diagnosis is by blood culture
  • treatment: benznidazole


Now for some low potassium....

MRCP revision battle 55.2: Hypokalaemia

Hypokalaemia is defined as K <3.5mmol; if <2.5mmol it is severe.


Symptoms/signs include:
  • muscle weakness
  • hypotonia
  • cramps
  • tetany
  • worsening of dig toxicity
  • cardiac arrhythmias

ECG may show:
  • small/inverted T waves
  • U waves
  • long PR
  • depressed ST

Causes of hypokalaemia


Low K with hypertension
  • raised plasma renin
    • Cushings
    • renin-secreting tumour
  • low plasma renin

Low K without hypertension


On to cryoglobulins...

    MRCP revision battle 55.3: Cryoglobulins

    Cryoglobulins are immunoglobulins that undergo reversible precipitation at 4c and dissolve when warmed to 37c.

    Cryoglobulins may be IgG, IgM or IgA.

    One third of cases are idiopathic.



    Type 1 cryoglobulinaemia
    • monoclonal
    • high titres, usually >5mg/ml
    • associated with:
      • myeloma
      • Waldenstroms
    • features include vasculitis, ulceration and Raynaud's

    Type 2 cryoglobulinaemia
    • mixed mono and polyclonal
    • titres usually >1mg/ml
    • associated with:
      • RA
      • sjogrens
      • lympoma
      • CLL
      • hep C
      • HIV
    • features include vasculitis, mesangiocapillary GN


    Type 3 cryoglobulinaemia
    • mixed polyclonal
    • associated with:
      • RA
      • sjogrens
      • SLE
    • features include purpura, GN, arthritis


    Now on to a similar but distinct topic...

    MRCP revision battle 55.4: Cold agglutinins

    Cold agglutinins are molecules, usually IgM, which act against red cells agglutinising and haemolysing them at low temperatures.

    Symptoms of cold agglutinins include:
    • Raynauds
    • acrocyanosis
    • mild haemolytic anaemia

    Causes of cold agglutinins include:
    • idiopathic
    • CLL
    • lymphoma
    • mycoplasma
    • coxsachie
    • mononucleosis
    • HIV

    Management is to avoid cold weather.



    Now to diversify to neurology....

    MRCP revision battle 55.5: Lateral medullary syndrome

    Lateral medullary syndrome is a condition in which a patient has a set of symptoms as a result of insult to the medulla.

    Lateral medullary syndrome is usually due to PICA or vertebral artery occlusion.


    Features include:
    • cerebellar signs
    • contralateral pain and temperature sensation loss
    • ipsilateral Horners
    • ipsilateral loss of pain and temperature sensation on face
    • ipsilateral paralysis of palate, pharynx and cords


    On to some vision loss...

    MRCP revision battle 55.6: Purtscher retinopathy

    Purtscher's retinopathy is characterised by cotton wool spots on fundoscopy with sudden detioration in vision.


    It is classically associated with head trauma or chest trauma.

    Other associations include:
    • pancreatitis
    • fat embolism
    • amniotic fluid embolism
    • vascular diseases

    There is no treatment.


    Finally - optic atrophy...

    MRCP revision battle 55.7: Optic atrophy

    Optic atrophy is loss of fibres of the optic disc.  It is characterised by decreased vision (particulary loss of colour vision) and a pale disc on fundoscopy.


    Causes include:


    Congenital:

    Acquired:
    • MS
    • papilloedema
    • glaucoma
    • ischaemia
    • B6, B12, folate deficieny
    • lead poisoning
    • arsenic poisoning
    • methanol
    • ethambutol
    • isoniazid
    • chloramphenicol