Born within seconds of each other but rare condition puts them worlds apart

LIKE any set of twins, little Neve and Erin Mortimer are two of a kind - but Neve is one in a billion.

The girls were born just seconds apart after IVF treatment, but now their lives are worlds apart.

The four-year-olds from Aberdeen share the same fair hair, blue eyes and smile. But Neve is one of only a handful of children in the world to suffer from the extremely rare chromosome condition Ring 18 Mosaicism.

The condition means that Neve's development lags behind that of Erin and other children her age and when her sister starts school in the summer, she will remain in nursery.

Their mother, Fiona Mortimer, 38, said: "We started to notice there were developmental differences in the girls between the ages of one and two.

"Erin was the first to sit up, crawl and walk while Neve lagged behind. Erin will just sit and chatter away articulately, but Neve has the verbal skills of a two-year-old. Neve is a very happy, sociable little girl who wants to play with other children, but they struggle to understand her."

The twins' father, Derek Mortimer, 46, added: "Neve's operating system is slow. If you compared it to a computer, Neve is Windows 95 and Erin is Windows 7."

A major hurdle for the Mortimers is the limited awareness of the condition. Mr Mortimer said: "The hardest thing is that there is nothing much to guide the medical professionals.

"There was little they could tell us about Neve's condition when she was diagnosed. We had to find out about it for ourselves."

The family have registered their daughter with the world's leading centre for research into the condition based at the University of Texas.