Table 3. [MEN1 Allelic Disorders]. - GeneReviews®

Disorder	MOI	Clinical Characteristics / Comments
MEN1-related familial isolated hyperpara- thyroidism (FIHP)	AD	FIHP is characterized by parathyroid adenoma or hyperplasia w/o other assoc endocrinopathies. MEN1 germline pathogenic variants have been reported in 20%-57% of families w/FIHP. ¹ In families w/MEN1-related FIHP, 38% of pathogenic variants are missense ‒ vs MEN1, in which missense variants account for 20% of cases. ² MEN1 nonsense variants are found in only 5% of families w/FIHP ‒ vs 23% in families w/MEN1. Of note, in 1 family w/FIHP w/an intronic MEN1 pathogenic variant & no clinical evidence of hyperparathyroidism-jaw tumor syndrome, the mother of the proband (genetic status unknown, but likely w/the same pathogenic variant as the proband) died of parathyroid carcinoma. ³ Thus, in contrast to MEN1 (in which risk for parathyroid carcinoma does not appear to be ↑), FIHP may be assoc w/↑ risk for parathyroid carcinoma (see also Differential Diagnosis).
Familial pituitary tumor	AD	MEN1 pathogenic variants have been identified in <1% of index cases w/familial pituitary tumor. ⁴

Disorder

MOI

Clinical Characteristics / Comments

MEN1-related
familial
isolated
hyperpara-
thyroidism
(FIHP)

FIHP is characterized by parathyroid adenoma or hyperplasia w/o other assoc endocrinopathies. MEN1 germline pathogenic variants have been reported in 20%-57% of families w/FIHP. ¹ In families w/MEN1-related FIHP, 38% of pathogenic variants are missense ‒ vs MEN1, in which missense variants account for 20% of cases. ² MEN1 nonsense variants are found in only 5% of families w/FIHP ‒ vs 23% in families w/MEN1. Of note, in 1 family w/FIHP w/an intronic MEN1 pathogenic variant & no clinical evidence of hyperparathyroidism-jaw tumor syndrome, the mother of the proband (genetic status unknown, but likely w/the same pathogenic variant as the proband) died of parathyroid carcinoma. ³ Thus, in contrast to MEN1 (in which risk for parathyroid carcinoma does not appear to be ↑), FIHP may be assoc w/↑ risk for parathyroid carcinoma (see also Differential Diagnosis).

Familial
pituitary tumor

MEN1 pathogenic variants have been identified in <1% of index cases w/familial pituitary tumor. ⁴

From: Multiple Endocrine Neoplasia Type 1

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

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