The term 'hypertrophy' means overgrowth and 'hemi-' means half, therefore the term hemihypertrophy means an overgrowth of one half of the body. It is characterised by a greater than 5% difference between the left and right side of the body.

It may involve one finger, one limb, one side of the face, one side of the tongue, one side of the chest or abdomen or any combination of the above. Unequal limb lengths may create walking difficulties.

The condition can be a benign familial trait or it may occur sporadically with no preceding family history.

Children with hemihypertrophy require regular paediatric assessment because some proceed to develop abdominal tumours. Some may develop a Wilm's Tumour or nephroblastoma, which is the commonest abdominal tumour in children. This tumour develops in the kidney and can grow quite large. If detected early it has a good prognosis.

Other children may develop a hepatoblastoma, which is a tumour of the liver. This can also grow quite large. The paediatric surveillance needs to be conducted over several years until it is clear that the child is no longer at risk.

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