- Familial isolated hyperparathyroidism is rarely caused by germline mutation in HRPT2, the gene for the hyperparathyroidism-jaw tumor syndrome. Simonds, W.F., Robbins, C.M., Agarwal, S.K., Hendy, G.N., Carpten, J.D., Marx, S.J. J. Clin. Endocrinol. Metab. (2004)