Multiple endocrine neoplasia 2A due to a unique C609S RET mutation presents with pheochromocytoma and reduced penetrance of medullary thyroid carcinoma.
OBJECTIVE
We have identified a large kindred with multiple endocrine neoplasia 2A (MEN 2A) due to a mutation at RET codon 609 that results in a cysteine to serine substitution, a mutation previously identified in only one case in the literature. We characterized the clinical phenotype of the kindred and the biochemical mechanism of this new mutation.


METHODS
The index case, a 42-year-old woman, presented with pheochromocytoma. We screened 29 family members for the presence of the mutation. Of the 15 mutation-positive family members, 11 agreed to undergo further evaluation by physical examination, calcium and pentagastrin-stimulated calcitonin levels, measurement of urinary metanephrines, adrenal imaging and serum calcium levels. Biochemical characterization of the mutation was by transient transfection of human neuroblastoma cells and Western blot analysis.


RESULTS
This kindred demonstrated an inheritance pattern consistent with autosomal dominant pheochromocytoma. Strikingly, no clinically evident case of medullary thyroid cancer (MTC) was observed among mutation-positive family members. Thyroidectomy in six cases revealed C-cell hyperplasia in all and microscopic MTC in two cases. Transfection experiments using human neuroblastoma cells showed that the mutant RET, unlike the wild-type receptor, is constitutively phosphorylated in the absence of ligand, and thus resembles other previously characterized MEN 2A mutations.


CONCLUSIONS
The identification of a new mutation causing a MEN 2A phenotype that features pheochromocytoma and the surprising absence of clinically apparent MTC has significant implications for carriers of this mutation and provides further insights into the genotype-phenotype correlation in MEN 2A.
Kinlaw
William B
WB
Department of Medicine, Division of Endocrinology and the Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH 03756 , USA. william.b.kinlaw@dartmouth.edu
Scott
Sarah M
SM
Maue
Robert A
RA
Memoli
Vincent A
VA
Harris
Robert D
RD
Daniels
Gilbert H
GH
Porter
Donna M
DM
Belloni
Dorothy R
DR
Spooner
Edward T
ET
Ernesti
Manfred M
MM
Noll
Walter W
WW
D000293:Adolescent; D000328:Adult; D002116:Calcitonin / Q000097:blood; D002118:Calcium; D018276:Carcinoma, Medullary / Q000235:genetics* / Q000378:metabolism; D002395:Catecholamines / Q000652:urine; D002648:Child; D003062:Codon; D005260:Female; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000652:urine; D008875:Middle Aged; D018813:Multiple Endocrine Neoplasia Type 2a / Q000175:diagnosis* / Q000235:genetics; D010375:Pedigree; D010418:Pentagastrin; D010673:Pheochromocytoma / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D012150:Polymorphism, Restriction Fragment Length; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013961:Thyroid Gland / Q000473:pathology; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism; D014642:Vanilmandelic Acid / Q000652:urine
D002395:Catecholamines; D003062:Codon; D008676:Metanephrine; D014642:Vanilmandelic Acid; D002116:Calcitonin; D051096:Proto-Oncogene Proteins c-ret; D010418:Pentagastrin; D002118:Calcium