Sunday 14 November 2010

MRCP revision battle 49.1: Homocystinuria

Today is back to being a mixed set of battles with some familiar topics and some utterly unusual ones...


MRCP revision battle 49.1: Homocystinuria
MRCP revision battle 49.2: Nail-patella syndrome
MRCP revision battle 49.3: Golfers and Tennis Elbow
MRCP revision battle 49.4: Whipples disease
MRCP revision battle 49.5: Hypermagnesaemia
MRCP revision battle 49.6: Osteoporosis
MRCP revision battle 49.7: Osteogenesis Imperfecta




MRCP revision battle 49.1: Homocystinuria


Homocystinuria is an autosomally recessive inherited condition in which there is decreased activity of cystathionine beta synthase resulting in accumulation of homocysteine and methionine which interferes with collagen cross-linkage.


Features include:
  • Marfanoid body habitus
  • spontaneous retinal detachment
  • downwards lens dislocation
  • osteoporosis
  • venous and arterial thrombosis
  • low IQ

Diagnosis is with the cyanide nitroprusside test which detects elevated urinary homocysteine.


Treatment is:
  • methionine restriction
  • cysteine supplements
  • pyridoxine supplements

Now to nail-patella syndrome...

MRCP revision battle 49.2: Nail-patella syndrome

Nail-patella syndrome occurs as a possible answer in a fair few MRCP questions so an insight into it is helpful...


Nail-patella syndrome affects 1 in 50,000

It is characterised by:
  • nail abnormalities, classically loss of the ulnar half of the thumb nail
  • small patella
  • boney spines over posterior iliac crests (70%)
  • renal abnormalities (30-50%)
  • over-extension of joints

On to some elbows...

MRCP revision battle 49.3: Golfers and Tennis Elbow

Golfer's Elbow
  • medial epicondylitis
  • pain worse on pronating forearm/ wrist flexion
  • may have an assocaited ulnar neuropathy

Tennis Elbow
  • lateral epicondylitis
  • pain worse on elbow/wrist extension
  • usually lasts 6 to 12 weeks
  • commoner than Golfer's elbow


Both are treated with:
  • ice
  • NSAIDs
  • ? corticosteroid injection
  • ?physio

Back to the world of esoteric medicine...

MRCP revision battle 49.4: Whipples disease

Whipple's disease is a rare cause of GI malabsorption.  It is caused by a gram positive bacterium Tropheryma whippelei.


Presentation is:
  • weight loss
  • arthralgia
  • diarrhoea
  • malaise
  • fever

Other symptoms may occur in relation to the malabsorption, for example signs of hypocalcaemia or vitamin C deficiency.


Possible clinical signs include:
• lymphadenopathy
• perioral hyperpigmentation


Cardiac involvement can result in an endocarditis, and CNS involvement can cause a reversible dementia.


It is commonest in males (9:1) and is associated with HLA B27.


Treatment is 2 weeks IV ceftriaxone then oral co-trimoxazole for one year.


Now for some excess magnesium...

MRCP revision battle 49.5: Hypermagnesaemia

Hypermagnesaemia generally becomes clinically relevant above 4mmol


Symptoms and signs include:
  • lethargy
  • nausea
  • areflexia
  • hypotension
  • heart block
  • bradycardia
  • double vision

Treatment is with IV calcium.


Next up: osteoporosis

MRCP revision battle 49.6: Osteoporosis

Osteoporosis literally means 'porous bone'.


It is diagnosed by DEXA scan:
  • T to -1 SD = normal
  • T -1 to -2.5 SD = osteopenia
  • T below -2.5  SD = osteoporosis


Fracture risk is increased by 2x with each standard deviation of the T score.

Common fracture sites include:
  • vertebrae and neck of femur = trabecular bone
  • distal radius and humerus = cortical bone


Factors increasing the risk of OP include:
  • being slim
  • smoker
  • alcoholic
  • inactive
  • old
  • steroid use
  • early menopause
  • thyrotoxicosis
  • primary biliary sclerosis
  • cushings

Primary prevention of OP is with alendronate.



Now to the final battle of the day, osteogenesis imperfecta

MRCP revision battle 49.7: Osteogenesis Imperfecta

Osteogenesis Imperfecta is an autosomal dominant inherited condition in which there is abnormal and or insufficient type 1 collagen synthesis.


This results in:
  • bone fractures
  • blue sclerea
  • deafness secondary to otosclerosis
  • muscle weakness


The photo below demonstrates the classical blue sclera  (from wiki commons, posted by Dr Fred)





There is no cure, so treatment is trying to prevent bone fractures.