Amyloid Goiter as the First Recognizable Manifestation of Immunoglobulin Light Chain Amyloidosis

Abstract

Clinically apparent thyroid enlargement due to massive amounts of amyloid deposition, known as amyloid goiter, is rare. Endocrinologists should become familiar with this manifestation of systemic amyloidosis, which may be diagnosed by Congo red staining of the specimen obtained by fine-needle aspiration. We describe a 70-year-old man who presented with a slowly enlarging goiter. It was asymptomatic, predominantly left-sided, nontoxic, and multinodular with atypia of undetermined significance (Bethesda System category III) by cytology. The goiter tested negative using the ThyraMIR miRNA Gene Expression Classifier kit (eviCore Healthcare, Bluffton, SC). Left thyroid lobectomy produced a 220-g specimen with nodular hyperplasia and prominent amyloid deposition confirmed by Congo red staining. Liquid chromatography tandem mass spectrometry detected a peptide profile consistent with light chain amyloid deposition of the lambda type, formerly called primary amyloidosis. In retrospect, he had been diagnosed with restrictive cardiomyopathy, cardiac conduction system disease, coronary artery disease, non-nephrotic range proteinuria, and chronic kidney disease, which had been attributed to his longstanding type 2 diabetes mellitus. Extensive workup subsequently demonstrated cardiac amyloidosis and monoclonal gammopathy of unknown significance, consistent with light chain amyloidosis. Amyloid goiter should be included in the differential diagnosis of enlarging goiters with Bethesda System category III cytology in patients with monoclonal gammopathy of uncertain significance, clinical manifestations of systemic amyloidosis, or known diagnosis of monoclonal cell dyscrasia.