A Kiwi student, who sends up to 100 text messages a day on her mobile phone, has been diagnosed with the country's first known case of text-messager's thumb.

The 20-year-old has texting tenosynovitis, an inflammation of the tendons in the thumb caused by constant text messaging.

There have been only two other reported cases of the ailment - a school-aged child in Singapore and a 13 year-old girl in Australia.

Authors of the journal report published in the Sunday Star-Times say it's likely tenosynovitis is more common than thought given the popularity of texting.

- AAP