MON-469 Rapidly Expanding Thyroid Goiter as the First Manifestation of Systemic Amyloidosis

INTRODUCTION Amyloidosis is a condition manifesting with extracellular tissue deposition of fibrils of low molecular weight proteins. In Ig light chain amyloidosis (AL), the deposition of Ig light chains can cause organ dysfunction, and patients can have involvement of a range of organs including kidney (70%), liver (70%), heart (60%), peripheral nerves (20%), the tongue, skin, and the coagulation system (1). We describe a unique case of AL amyloidosis, which first presented with thyroid involvement. CLINICAL CASE A 78 year old female patient with hx of small lymphocytic lymphoma and normal thyroid function presented with an expanding symptomatic goiter and compressive symptoms (positive Pemberton sign) for which a total thyroidectomy was performed. Pathology showed Congo red-birefringent amyloid deposition. SPEP showed a small amount of M protein, with circulating monoclonal free lambda light chain on immunofixation. The free kappa lambda light chain ratio was low (0.04) with an elevated serum free lambda light chain (283.93). Mass spectrometry confirmed AL light chain amyloidosis - lambda type. A work up was initiated to assess other organ involvement. Echocardiogram showed mild thickening of left ventricle with a preserved EF and EKG showed low voltage in limb leads. Creatinine (1.05) was minimally elevated from baseline with minimal proteinuria (396 mg/24 hours). Alkaline phosphatase, APTT, and PT were normal. The patient described tongue enlargement and scalloping of the tongue from tooth impingement was seen. Biopsies of tongue and bone marrow also showed amyloidosis thereby securing the diagnosis of systemic amyloidosis, and chemotherapy was initiated. CONCLUSION This case illustrates the importance of considering amyloid goiter in the differential for a rapidly enlarging thyroid, even when there is no history of amyloidosis. Although extremely uncommon, a few case reports have described amyloid goiter. In our case, thyroid AL was the initial presentation of systemic amyloidosis. Because disease can be localized or systemic, work up should include an assessment for the presence of a monoclonal gammopathy and an assessment for amyloid mediated organ dysfunction. Tissue should be sent for amyloid typing – there are 35 different proteins known to form amyloid fibrils and prognosis and treatment depends on amyloid type (2). Typing using Liquid Chromatography-Tandem Mass Spectrometry, is the most sensitive and specific methodology, though, in experienced hands, typing by immune histochemistry is an option. REFERENCES 1. Rajkumar, S.V., Dispenzieri, A. Clinical presentation, laboratory manifestations, and diagnosis of immunoglobulin light chain (AL) amyloidosis. Uptodate. 2019. 2. Winter, M., Tholey, A., Kristen, A., Röcken, C. MALDI Mass Spectrometry Imaging: A Novel Tool for the Identification and Classification of Amyloidosis. Proteomics 2017, 17, 1700236.