title: Thymic hyperplasia in patients with Graves' disease.
abstract: BACKGROUND
  Graves' disease (GD) is commonly associated with other autoimmune conditions, and there is also a rare but well documented association between GD and thymic hyperplasia (TH). It is hard to say the real frequency of this latter association because most cases remain asymptomatic and are consequently not thoroughly investigated.
  
  
  METHODS
  We reviewed the literature on GD-related thymus enlargement and found 107 cases published to date. Thymic cancer was only documented in four patients, while the majority of cases were diagnosed as TH. The causative mechanisms behind TH associated with GD have yet to be fully elucidated. Several studies support the hypothesis of a TSH receptor antibody (TRAb) mediating thymic enlargement.
  
  
  RESULTS
  We report on a female GD patient with an incidentally discovered anterior mediastinal mass. Our case is not consistent with the hypothesis of a TRAb-mediated mechanism because the thymus reached its largest volume at the onset of GD and shrank during remission of GD under medical treatment, despite persistently positive TRAb levels.
  
  
  CONCLUSIONS
  We support the hypothesis that two different pathogenic mechanisms might be responsible for thymus enlargement: thymic cortical tissue expansion seems to be due to a hyperthyroid state, while lymphoid hyperplasia appears to correlate with immune abnormalities underlying GD.
authors.affiliation: Endocrine Unit, Department of Medicine, University of Padova School of Medicine, Via Ospedale Civile 105, 35128, Padova, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Dalla Costa
authors.forename: F A
authors.initials: FA
authors.lastname: Mangano
authors.forename: C
authors.initials: C
authors.lastname: Betterle
mesh_terms: D000293:Adolescent; D003937:Diagnosis, Differential; D005260:Female; D006111:Graves Disease / Q000150:complications* / Q000175:diagnosis*; D006801:Humans; D013952:Thymus Hyperplasia / Q000150:complications* / Q000175:diagnosis*