Sunday, 12 September 2010

MRCP revision battle 9.1: Lyme Disease

Working and revising really does feel rather relentless.  I keep thinking of the pop song "and the beat goes on..." - somehow it seems appropriate for the continuous dedication work plus MRCP revision requires!  Anyway, what revision battles does today bring?

MRCP revision battle 9.1: Lyme disease
MRCP revision battle 9.2: Gout
MRCP revision battle 9.3: Pseudogout
MRCP revision battle 9.4: Craniopharyngioma
MRCP revision battle9.5: Pneumothorax

MRCP revision battle 9.1: Lyme disease

Lyme disease, named after the place in America where the condition was first noted, is a condition caused by the spirochaete borrelia burdorferi.  

It is spread by tic bites, with certain areas (such as northern America) being higher risk than, for example, Surrey.  However, it is found in the UK and it is important to note the majority of patients will not remember the bite itself.

Signs, symptoms and complications associated with Lyme disease are multitude and vague, including:
  • malaise
  • fever
  • muscle pain
  • joint swelling
  • decreased cognition
  • encephalitis
  • meningitis
  • lymphadenopathy
  • cranial nerve palsies (MRCP likes bilateral facial nerve palsy for some reason)
  • neuropathy
  • skin conditions

The classical skin condition associated with Lyme disease is erythema chronicum migrans, which is a spreading erythematous rash which then clears centrally but leaves a spot in the middle (click here for a picture).

A rarer skin condition is acrodermatitis chronica atrophicans, which occurs late in infection and eventually results in atrophic skin that is thin like cigarette paper.

Another rarer skin manifestation is borrelial lymphocytoma, which is a blue-red discoloration of the ear lobe.

Investigation is usually ELISA/PCR.
If the question throws in a CSF sample look for slightly raised protein and lymphocytosis.

Treatment of the rash only is doxycycline.  More serious disease may require IV ben pen/a 3rd generation cephalosporin. 

There is of course far more to learn about Lyme disease should you be so inclined, but if you're content with the barer MRCP-bones of it lets move on to battle 9.2, gout.