A courageous schoolgirl is the only person in the world to have been diagnosed with a severe growth condition that is so rare it has no name.

Melanie Gardner, 34, was alarmed when she realised how much smaller her daughter Harlow, six, was than her peers – while she played at nursery. Worried Melanie and her husband, Peter, 37, a gym commercial director, took Harlow to the GP and she was referred for tests with specialists.

The results revealed little Harlow had a rare genetic mutation – a…