Charles Byrne was 2.4m tall, and died at an age of 22 after earning his living from street shows.

It has been found out by researchers that a mutant gene was responsible for the most famous giant in medical history and this gene had first shown its presence about 1500 years ago and in the same region of Northern Ireland where Charles was born, it is still causing excessive growth in families.

Small areas still have giants but the location is disclosed to avoid the attention from other people.

About four families still were seen having the same genetic mutation and three patients were seen who were in the early stages of excessive growth but they were unaware of the fact that they were affected.

In recent generations, these families have been responsible for about six giants and few others who have shown signs of growth abnormalities.

If the pituitary gland has a benign tumor, gigantism is caused as excessive growth hormone is released by this gland. A child can grow very tall if this development takes place early but abnormal growth of various parts like feet, hands and face etc can be seen in adulthood, which is known as acromegaly.