Doctors are worried a painful bone disorder rickets is making a comeback in New Zealand

The rare disease is caused by a lack of calcium, phosphorous or vitamin D - with harrowing symptoms including seizures, bow-leggedness, and an increased risk of spontaneous broken bones.

A new survey, which Otago's New Zealand Paediatric Surveillance Unit has been running since September, has already turned up 20 cases.

Dunedin Hospital paediatric endocrinologist Ben Wheeler worries this is just the tip of the iceberg.

He's also concerned none of the cases his team saw were prescribed the recommended vitamin D supplements.