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.