Thirty such MEN1 mutations have been reported in patients with FIHP, and 15 of these mutations are identical to those reported in MEN1 patients and include intragenic deletions, gross deletions, intragenic insertions, missense, nonsense and splice site mutations (4, 5); thereby indicating that the same MEN1 mutations may cause MEN1 or FIHP in unrelated families. Here, MEN1 is linked to familial isolated hyperparathyroidism.