title: Multiple endocrine neoplasia 2A due to a unique C609S RET mutation presents with pheochromocytoma and reduced penetrance of medullary thyroid carcinoma.
abstract: 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.
authors.affiliation: Department of Medicine, Division of Endocrinology and the Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH 03756 , USA. william.b.kinlaw@dartmouth.edu
authors.forename: William B
authors.initials: WB
authors.lastname: Kinlaw
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Scott
authors.forename: Robert A
authors.initials: RA
authors.lastname: Maue
authors.forename: Vincent A
authors.initials: VA
authors.lastname: Memoli
authors.forename: Robert D
authors.initials: RD
authors.lastname: Harris
authors.forename: Gilbert H
authors.initials: GH
authors.lastname: Daniels
authors.forename: Donna M
authors.initials: DM
authors.lastname: Porter
authors.forename: Dorothy R
authors.initials: DR
authors.lastname: Belloni
authors.forename: Edward T
authors.initials: ET
authors.lastname: Spooner
authors.forename: Manfred M
authors.initials: MM
authors.lastname: Ernesti
authors.forename: Walter W
authors.initials: WW
authors.lastname: Noll
mesh_terms: 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
chemical_list: D002395:Catecholamines; D003062:Codon; D008676:Metanephrine; D014642:Vanilmandelic Acid; D002116:Calcitonin; D051096:Proto-Oncogene Proteins c-ret; D010418:Pentagastrin; D002118:Calcium