Localized thymic amyloidosis associated with MG has not been reported to date. Keywords:Amyloidosis, Thymus, Mediastinum, Myasthenia Gravis == INTRODUCTION == Amyloidosis is a large group of diseases characterized by the deposition of misfolded extracellular fibrillar proteins in various organs and tissues. of fragments of Ig light chains (AL) that are produced by plasma cells. It can occur in association with clonal B-cell dyscrasia or otherwise benign conditions, as a systemic or localized form (2,3). Secondary amyloidosis consists of the deposition of amyloid fibril proteins (AA) that are derived from circulating acute-phase reactants. That condition is caused by a number of chronic inflammatory diseases or neoplasms, which is typically a systemic disease (4-7). There are other protein subtypes CID-1067700 that have been identified but they are far less common (8). Amyloidosis also can be classified as a systemic disease (80%-90%) or as a localized disease (10%-20%) (9). Localized amlydoidosis may produce grossly detectable nodular masses, mostly in the upper respiratory tract (nasopharynx), lip, colon, skin, nails, and orbit (4,10). Localized amyloidosis presenting as a mediastinal mass, especially in the thymus, is rare (11). To date, there have been only two reported cases of localized thymic amyloidosis. One case that presented with rheumatoid arthritis was reported in Japan (11). The other case was reported in Korea; the patient did not have a notable past medical history or subjective symptoms (2). A case of localized thymic amyloidosis that was manifested as a mediastinal mass in a patient with myasthenia gravis (MG) is reported here. == CASE DESCRIPTION == A 46-yr-old woman was referred to Chungbuk national university hospital for thymectomy in February, 2013. Two months ago, she admitted for first developed ptosis, weakness in the neck, and dyspnea, and was diagnosed with acetylcholine receptor-positive MG. A chest computed tomography (CT) scan revealed a mass with calcification CID-1067700 in the anterior mediastinum, which was suggestive of thymoma (Fig. 1). While undergoing cholinesterase inhibitor (Mestinon) therapy, the patient developed a myasthenic crisis and was given immunoglobulin (Ig) therapy for 5 days under managed ventilator care. Treatment with corticosteroids then continued for a month. After the symptoms regressed, the patient was discharged. She visited the hospital again 2 months later for resection of the mediastinal mass. Given the clinical impression of thymoma-associated MG, mass resection and total thymectomy were performed. == Fig. 1. == Computed tomography reveals an anterior mediastinal mass with calcifications (arrow). Macroscopically, the resected mass, which measured 431.5 cm, was a relatively well-demarcated nodule that was surrounded by fat. The cut section was hard, yellow to gray, and calcified (Fig. 2). Microscopically, the mass was composed of amorphous eosinophilic hyaline materials surrounding islands of thymic tissues (Fig. 3). Stromal calcification and ossification were noted. The associated inflammatory reaction consisted of small lymphocytes and occasional plasma cells. These eosinophilic substances displayed apple-green birefringence under polarized light microscopy after Congo red staining (Fig. 4). Immunohistochemical analysis revealed that they were positive for kappa and lambda light chains and negative for serum amyloid A. These findings were consistent with primary (light chain) amyloidosis. Further examinations were done to rule out plasma cell dyscrasia or lymphoproliferatvie disorder. The serum IgG, IgA, and IgM levels were normal. Serum and urine protein electrophoresis did not detect any abnormal bands. Serum and urine immunoelectrophoresis did not indicate any definite abnormalities. The serum calcium levels were also within normal limits. To screen for systemic amyloidosis, complete blood count, erythrocyte sedimentation rate, echocardiogram, basic metabolic and biochemical panel, and liver function tests were performed. All returned values that were within normal limits. This suggested that the thymic amyloidosis was localized. CID-1067700 Therefore, the final diagnosis of primary localized amyloidosis that only involved the thymus was made. The symptoms of MG were relieved dramatically after thymectomy. == Fig. 2. == The resected mass is hard and has a lobulated contour. The cut surface is yellow to gray coloured with calcification. == Fig. 3. == Histopathology of the mass, HE stained. (A) The mass consists of amorphous eosinophilic hyaline substances that surround islands of thymic cells, 40. (B,C) Calcification and ossification are present in the amyloid deposits, 40. == Fig. 4. == Apple-green birefringence is definitely mentioned under polarized light microscopy after Congo reddish staining. == Conversation == Amyloidosis is definitely a rare medical disorder that is defined as the progressive build up Rabbit Polyclonal to KANK2 of amyloid deposits at a systemic or organ-specific level (8). Localized amyloidosis usually carries a better prognosis than the systemic form (12)..
