Endocrine Abstracts

The clinical diagnosis of MEN1 is established when a proband manifests at least two of the manifestations of the triad (Primary Hyperparathyroidism (PHPT), Pituitary adenoma, Gastroenteropancreatic Neuroendocrine Tumor (GEP-NET)). Typically, it is a familial disease (F-MEN1), while in about 10% of cases the disease is sporadic. In sporadic forms (S-MEN1), up to 70% of patients may exhibit a negative genetic analysis (MEN1-negative). These patients seem to have distinct features compared to those who carry MEN1 mutation (MEN1-positive). This study aims to assess the clinical phenotype of MEN1-negative and MEN1-positive patients in terms of endocrine and non-endocrine manifestations and survival. This is a retrospective study including 187 patients (105 index cases and 82 relatives) with S-MEN1 and F-MEN1 followed at our clinic from January 1993 to January 2023. One hundred-forty (75%) were MEN1-positive and 47 (25%) MEN1 negative. The median observation time was 120 months (IQR 60-190) for MEN1-positive and 122 months (IQR 75-178) for MEN1-negative. MEN1-positive exhibited a significantly lower mean age of onset of PHPT (36.3+14.2 vs 49.5+13 years; P<0.00001), pituitary adenoma (36.2+13.5 vs 44.2+14.4 years; P=0.006), and GEP-NET (39.7+13 vs 47.8+11 years; P=0.008). None of the MEN1-negative patients had GEP-NET before 30 years. MEN1-positive patients also displayed a significantly lower age of onset of the first (36+14.3 vs 46+14.8 years; P<0.0001), second (39.7+14.1 vs 50.2+13.1 years; P<0.0001), and third (42+14 vs 54.4+11.4 years; P=0.001) endocrine manifestations. A higher prevalence of GEP-NET was found in MEN1-positive than MEN1-negative (61% vs 29%; P=0.02). Additionally, none of the MEN1-negative presented metastatic GEP-NET (0% vs 16%; P<0.001). Although no difference in the median number of manifestations was observed between the two groups (P=0.06), MEN1-positive exhibited a greater distribution of the number of manifestations compared to MEN1-negative (1 to 6 vs 2 to 4, respectively; P=0.005). MEN1-positive had a higher prevalence of lipomas (P=0.01) and angiofibromas (P=0.01) compared to MEN1-negative. No difference in survival rate was found between the two cohorts. However, in MEN1-negative patients none died for MEN1-related causes, whereas in MEN1-positive 7 patients died for MEN1-related causes. The overall findings suggest that MEN1-negative patients exhibit a less aggressive phenotype than MEN1-positive. Consequently, they may benefit from a less intensive follow-up. This underscores the need to update the MEN1 guidelines to differentiate the diagnostic and therapeutic workout in MEN1-negative and MEN1-positive.