Sunday, March 13, 2016

Diseases and their twins.

There a few diseases which quite resemble an other disease in presentation and sometimes pathology.Here's a list I made-

1. Wolf-Parkinson-White and
    Lown-Ganong-Levine syndrome-

    -What's similar?
     The tachycardia, short PR   
      interval, pre- excitation

   -What's different?
     While in WPW syndrome,the
     culprit is a naughty extra pathway,
     the bundle of Kent, in LGL the AV
     node itself is naughty.(The
     hypothesized bundle of James 
     hasn't been discovered yet)
     Conduction through the AV node
     occurs rapidly.
    
     ECG findings- WPW syndrome has
     a short PR interval and a Delta
     wave on the QRS complex. No
     Delta waves occur in the LGL
     syndrome.
    
     Also, the risk of sudden death
     remains lower in LGL syndrome.


2. Myasthenia Gravis and Lambert
    Eaton syndrome.

    -What's similar?
     The muscle weakness.

   -What's different?
    Oh almost everything. In MG,
    autoantibodies are formed against
    the nicotinic receptors whilst in
    LEMS(Lambert Eaton myasthenic 
    syndrome), the antibodies are 
    against 'pre synaptic voltage 
    gated Calcium channels'.
   
     LEMS is mostly associated with
     underlying malignancies,
     making it a paraneoplastic
     syndrome.

      In contrast to MG, where
      distal musculature is affected
      the most, proximal musculature
      gets involved in LEMS. Arm
      muscles are frequently involved
      while MG prefers muscles of the
      leg.
     
      The autonomic nervous system
      also may be affected in LEMS.

     The most significant difference
     is that the strength actually
     improves on exertion in LEMS,
     known as 'Lambert's sign',  
     whereas in MG, weakness 
     prevails on repeated activity.


3. Multiple sclerosis and Devic's
   disease
   
     -What's similar?
     The demyelination and
     associated CNS symptoms.

     -What's different?
      Many things. The optic nerve
      and spinal cord are affected more
      commonly in Devic's. MS affects
      the CNS as a whole.

      Devic's runs a more serious
      course than MS, the morbidity
      after an attack is more severe
      compared to it.

     MS is a T cell mediated
     autoimmune disease while IgG
     antibodies mediate Devic's, more
     specifically the
     NMO(neuromyelitis optica)IgG.
     Oligoclonal bands are rare in
     Devic's, and disappear after
     an attack.

     Uhthoff's phenomenon, where
     symptoms worsen after exposure
     to higher temperatures,and the
     Lhermitte's sign, where sudden,
     shock like sensation travelling
     through the spinal cord is felt,
     occur more commonly in MS.

4.Plague and Tularemia.
    
     -What's similar?
       Those large, pus filled lymph
        nodes.
    
     -What's different?
       Everything.Francisella
       tularensis is the causative agent,
       ticks and arthropods are the
       vectors, rabbits are the source,
       so on and so forth!
     

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