While a number of studies report the frequency of all deaths that were due to non-MEN1-related deaths, there are relatively few data on the exact non-MEN1-related causes of death, and it has in general not been systematically studied. In most studies the exact causes of the non-MEN1-related deaths are not specifically stated, so it is in general more difficult to compare our data to that in the literature. In our 106 NIH MEN1/ZES patients the cause of death was determined in all cases, with 42% of the 24 deaths due to a non-MEN1-related death, and in the 227 MEN1/PET patients from the pooled literature, 34% of all the deaths (73/227 patients) were due to a non-MEN1-related cause of death. Whereas the mean overall percentage of deaths due to non-MEN1-related causes in the literature from 13 series54,57,78,88,129,150,217,251,254,289,378,379,444,448,465 was similar to the data in our 2 series (mean, 33% ± 7%), the percentage of all deaths due to a non-MEN1-related death varied widely in the different series from 0 to 72% of all the deaths reported (Table 13). In 4 series the percentage of all deaths due to non-MEN1-related deaths was <20%,57,217,254,289,367 and in 5 series >50%.54,78,88,378,379,448,465 This marked difference is not due to the time of reporting of the series, because the mean percentage of patient deaths reported due to a non-MEN1-related cause for the 4 series reported before the widespread use of proton pump inhibitors (prior to 1995),254,289,367,378,379,444,465 and the 9 series reported after their widespread use (after 1995) are similar54,57,78,88,129,150,217,251,448 (25 ± 10% vs 36 ± 9% all deaths due to non-MEN1-related death). These data demonstrate that approximately one-third of all deaths in MEN1 patients are due to a non-MEN1-related cause.