title: Discordant thymectomy in identical twins concordant for myasthenia gravis.
abstract: BACKGROUND
  Thymectomy is standard therapy fornonthymomatousmyasthenia gravis despite the absence of randomized clinical trials (1). Myasthenia gravis is uncommonly reported in monozygous twins; disease concordance occurs in approximately one third of such identical twin pairs; and treatment for myasthenia gravis, when described,is usually concordant in identical twin pairs (2).
  
  
  OBJECTIVE
  To report an 11-year clinical course of a pair of identical twins concordant for generalized acetylcholine receptor antibody–positive nonthymomatous myasthenia gravis in whom only 1 was treated with extended transsternal thymectomy.
  
  
  METHODS
  Twin A was a 19-year-old white woman who presented with an 8-week history of intermittent leg weakness, causing her to fall during activities, such as climbing stairs. On examination,she had moderately severe fatigable proximal muscle weakness and ptosis. Her weakness improved with intravenous edrophonium administration.Initial binding acetylcholine receptor antibody titer was 1.22 nmol/L (normal value, 0.03 nmol/L). Repetitive 2-Hz nerve(median, ulnar, and facial) stimulation studies demonstrated up to a 16% decremental response. Chest computed tomography showed residual thymic tissue without thymoma. An extended transsternal thymectomy was performed 11 weeks after the onset of symptoms.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Riggs
authors.forename: Laurie
authors.initials: L
authors.lastname: Gutmann
authors.forename: Jack E
authors.initials: JE
authors.lastname: Riggs
mesh_terms: D001323:Autoantibodies / Q000097:blood; D002800:Cholinesterase Inhibitors / Q000627:therapeutic use*; D004200:Diseases in Twins / Q000188:drug therapy* / Q000276:immunology / Q000601:surgery*; D004491:Edrophonium / Q000627:therapeutic use; D005260:Female; D006801:Humans; D009157:Myasthenia Gravis / Q000188:drug therapy* / Q000276:immunology / Q000601:surgery*; D011729:Pyridostigmine Bromide / Q000627:therapeutic use; D011950:Receptors, Cholinergic / Q000276:immunology; D012074:Remission Induction; D013934:Thymectomy; D014430:Twins, Monozygotic; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D002800:Cholinesterase Inhibitors; D011950:Receptors, Cholinergic; D004491:Edrophonium; D011729:Pyridostigmine Bromide