title: Thyrotoxic myopathy mimicking myasthenic syndrome associated with thymic hyperplasia.
abstract: A 41-year-old man with progressive limb weakness manifested fluctuating muscle weakness as seen in myasthenia gravis (MG). Laboratory investigations revealed hyperthyroidism without the complication of MG. Electrophysiological studies demonstrated abnormal features of neuromuscular transmissions resembling those of the Lambert-Eaton myasthenic syndrome rather than those of MG. A CT scan showed a mediastinal mass that suggested thymic hyperplasia which often complicates MG or hyperthyroidism. Medical treatment of hyperthyroidism resulted in resolution of MG-like symptoms and regression of thymic hyperplasia on CT concomitant with normalization of thyroid function. This case highlights the fact that careful investigations are needed to differentiate MG-like symptoms from genuine MG in cases of hyperthyroidism with thymic lesions.
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine.
authors.forename: Emiko
authors.initials: E
authors.lastname: Tsuda
authors.forename: Tomihiro
authors.initials: T
authors.lastname: Imai
authors.forename: Akihiro
authors.initials: A
authors.lastname: Matsumura
authors.forename: Shin
authors.initials: S
authors.lastname: Hisahara
authors.forename: Michio
authors.initials: M
authors.lastname: Nonaka
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Shiraishi
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Motomura
authors.forename: Shun
authors.initials: S
authors.lastname: Shimohama
mesh_terms: D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use; D003937:Diagnosis, Differential; D006111:Graves Disease / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008297:Male; D008713:Methimazole / Q000627:therapeutic use; D018908:Muscle Weakness / Q000209:etiology*; D009157:Myasthenia Gravis / Q000175:diagnosis; D013952:Thymus Hyperplasia / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D013971:Thyrotoxicosis / Q000150:complications*
chemical_list: D013956:Antithyroid Agents; D008713:Methimazole