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A family of multiple endocrine neoplasia type 2A: genetic analysis and clinical features
1Third Department of Internal Medicine, Gifu University School of Medicine, Japan.
Abstract:
Since a heterozygous missense mutation of the RET proto-oncogene in the germline was found to cause multiple endocrine neoplasia type 2A (MEN 2A) in 1993, some 20 different mutations of this gene have been identified in MEN 2A kindreds. We report an MEN 2A family in which serine (AGC) substitutes for cysteine (TGC) at codon 618 in exon 10 of the RET proto-oncogene. The mutation was identified by sequencing PCR products of exons 10 and 11 in the proband. Since this mutation results in creation of a new cleavage site for Alu I restriction enzyme, most of the other members of the family were screened by digestion of the PCR product of exon 10 with this enzyme. Eleven of 20 subjects across four generations examined have the mutation of the RET proto-oncogene, and all of the adult gene carriers except one woman had MTC. Characteristics of this family are 1) pheochromocytoma has been found in only the proband, 2) no obvious hyperparathyroidism has been observed, and 3) the prognosis is favorable, with nobody dying of MEN 2A itself. Genetic analysis of MEN 2A is definitely useful and essential for screening of a MEN 2A family. It is very important to accumulate cases with MEN 2A and investigate the phenotype and the prognosis in each mutation.
Insights
Genetic analysis identified a new RET proto-oncogene mutation causing multiple endocrine neoplasia type 2A (MEN 2A). This discovery aids in screening MEN 2A families and understanding disease prognosis.
Area of Science:
- Endocrinology
- Human Genetics
- Oncology
Background:
- Multiple endocrine neoplasia type 2A (MEN 2A) is a hereditary disorder linked to germline mutations in the RET proto-oncogene.
- Over 20 distinct RET mutations have been identified in MEN 2A kindreds since its discovery in 1993.
Observation:
- A novel heterozygous missense mutation, cysteine to serine substitution at codon 618 in exon 10 of the RET proto-oncogene, was identified in an MEN 2A family.
- This specific mutation created a new Alu I restriction enzyme cleavage site, enabling efficient family screening via PCR product digestion.
Findings:
- Eleven out of 20 family members across four generations carried the identified RET proto-oncogene mutation.
- All adult gene carriers, except one woman, developed medullary thyroid carcinoma (MTC).
- Pheochromocytoma was observed only in the proband, and hyperparathyroidism was not evident. The family exhibited a favorable prognosis, with no deaths directly attributed to MEN 2A.
Implications:
- Genetic analysis of the RET proto-oncogene is crucial for effective screening and diagnosis of MEN 2A within affected families.
- Accumulating data on MEN 2A cases and correlating specific mutations with clinical phenotype and prognosis is essential for personalized patient management.
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