Table 5. [Differential Diagnosis of MEN1-Associated Clinical Features]. - GeneReviews®

Clinical Feature	Comments
Pituitary tumors	If single pituitary adenoma: (1) not likely to be assoc w/MEN1 if no other findings of MEN1 ¹; (2) responds better to medical therapy than MEN1-assoc pituitary tumors ¹ If multiple pituitary adenomas: see Table 3, Familial pituitary tumor
Zollinger-Ellison syndrome (ZES)	Sporadically occurring gastrinomas (1) more commonly pancreatic in origin ¹; (2) occur 1 decade later than gastrinomas in MEN1 ¹ 2 persons w/ZES & pathogenic variants in 2 cyclin-dependent kinase inhibitor genes (RPRD1A & CDKN1B) reported ¹ Gastrinomas may also be present in MEN4, TSC, & NF1.
Nonfunctioning neuroendocrine tumors	Affect 20%-55% of persons w/MEN1 May also be present in VHL (10%-17%) & NF1
Insulinoma	Peak age at onset ~1 decade later in those w/sporadic insulinomas ¹ Insulinomas may also be present in NF1.
Carcinoid tumors	When not assoc w/MEN1: usually occur in derivatives of the midgut & hindgut; are argentaffin positive; secrete serotonin (5-hydroxytryptamine); & have less severe course than MEN1-assoc thymic carcinoid tumors ¹ Assoc of gastric carcinoids & hyperparathyroidism appears to constitute distinct syndrome in genetically predisposed persons; should not be regarded as "atypical" or "incomplete" expression of MEN1. ¹
Facial angiofibromas	Also seen in TSC Age of onset in TSC: 3-4 yrs (vs in MEN1: <40 years)
Leiomyomas	May also be seen in w/Alport syndrome

Clinical Feature

Comments

Pituitary tumors

If single pituitary adenoma: (1) not likely to be assoc w/MEN1 if no other findings of MEN1 ¹; (2) responds better to medical therapy than MEN1-assoc pituitary tumors ¹
If multiple pituitary adenomas: see Table 3, Familial pituitary tumor

Zollinger-Ellison syndrome (ZES)

Sporadically occurring gastrinomas (1) more commonly pancreatic in origin ¹; (2) occur 1 decade later than gastrinomas in MEN1 ¹
2 persons w/ZES & pathogenic variants in 2 cyclin-dependent kinase inhibitor genes (RPRD1A & CDKN1B) reported ¹
Gastrinomas may also be present in MEN4, TSC, & NF1.

Nonfunctioning neuroendocrine tumors

Affect 20%-55% of persons w/MEN1
May also be present in VHL (10%-17%) & NF1

Insulinoma

Peak age at onset ~1 decade later in those w/sporadic insulinomas ¹
Insulinomas may also be present in NF1.

Carcinoid tumors

When not assoc w/MEN1: usually occur in derivatives of the midgut & hindgut; are argentaffin positive; secrete serotonin (5-hydroxytryptamine); & have less severe course than MEN1-assoc thymic carcinoid tumors ¹
Assoc of gastric carcinoids & hyperparathyroidism appears to constitute distinct syndrome in genetically predisposed persons; should not be regarded as "atypical" or "incomplete" expression of MEN1. ¹

Facial angiofibromas

Also seen in TSC
Age of onset in TSC: 3-4 yrs (vs in MEN1: <40 years)

Leiomyomas

May also be seen in w/Alport syndrome

From: Multiple Endocrine Neoplasia Type 1

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Adam MP, Feldman J, Mirzaa GM, et al., editors.

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