HPT-JT is caused by faults in the CDC73 gene. The CDC73 gene is a ‘tumour protection’ gene that helps to protect against benign and malignant (cancerous) tumours.
Everyone has two CDC73 genes (one from their mother, and one from their father). If one of the genes is not working, this is known as having a faulty CDC73 gene, or having a CDC73 mutation. People with a faulty CDC73 gene are known to have Hyperparathyroidism-jaw tumour syndrome.