J Korean Med Sci.  2014 Jan;29(1):145-148. 10.3346/jkms.2014.29.1.145.

Localized Thymic Amyloidosis Presenting with Myasthenia Gravis: Case Report

• Son SM
• Lee YM
• Kim SW
• Lee OJ

• KMID: 1796929
• DOI: http://doi.org/10.3346/jkms.2014.29.1.145

Abstract

A mediastinal mass was incidentally found on chest radiography in a 46-yr-old woman who had had myasthenia gravis (MG) for 2 months. Computed tomography revealed a 4-cm in size, well-defined, and lobulating mass with nodular calcification that was located in the thymus. Microscopically, the mass consisted of diffuse amorphous eosinophilic materials. These deposits exhibited apple-green birefringence under polarized light microscopy after Congo red staining. Immunohistochemical analysis revealed that they were positive for both kappa and lambda light chains and negative for amyloid A. A diagnosis of localized primary thymic amyloidosis was finally made. After thymectomy, the symptoms of MG were controlled with reduced corticosteroid requirements. Localized thymic amyloidosis associated with MG has not been reported to date.

Keyword

Amyloidosis; Thymus; Mediastinum; Myasthenia Gravis

MeSH Terms

Amyloidosis/complications/*radiography/*surgery
Calcinosis/*radiography/*surgery
Female
Humans
Immunoglobulin kappa-Chains/immunology
Immunoglobulin lambda-Chains/immunology
Mediastinum/radiography/surgery
Middle Aged
Myasthenia Gravis/*complications
Radiography, Thoracic
Thymectomy
Thymus Gland/radiography/surgery
Tomography, X-Ray Computed
Immunoglobulin kappa-Chains
Immunoglobulin lambda-Chains

Figure

• 

  Fig. 1 Computed tomography reveals an anterior mediastinal mass with calcifications (arrow).

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  Fig. 2 The resected mass is hard and has a lobulated contour. The cut surface is yellow to gray colored with calcification.

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  Fig. 3 Histopathology of the mass, HE stained. (A) The mass consists of amorphous eosinophilic hyaline substances that surround islands of thymic tissues, ×40. (B, C) Calcification and ossification are present in the amyloid deposits, ×40.

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  Fig. 4 Apple-green birefringence is noted under polarized light microscopy after Congo red staining.

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