A Case of Thyroid Amyloidosis Misrecognized as Subacute Thyroiditis

Abstract

Amyloid deposition in the thyroid is found in about 30-80% of the patients with primary or secondary amyloidosis. In a few patients with amyloidosis, the thyroid is enlarged and so called amyloid goiter occurs. The thyroid function usually remains normal, but occasionally hypothyroidism or thyrotoxicosis occurs in patients with thyroid amyloidosis. We have experienced one case of thyroid amyloidosis due to bronchiectasis and the patient developed painful goiter and transient thyrotoxicosis resembling subacute thyroiditis. Biopsies from the gastric antrum, duodenum, colon, kidney and thyroid were positive for deposition of amyloid. When patients have signs and symptoms of subacute thyroiditis, but they develop an unusual course, then the diagnosis of thyroid amyloidosis should be considered.

Amyloid goiter mimicking subacute thyroiditis on clinical and imaging findings: A case report

“…Known US findings of AG are a diffusely enlarged thyroid gland with markedly increased echogenicity, a finely homogenous echotexture, an appearance similar to that of ground glass, and marked posterior attenuation, consistent with diffuse fatty infiltration. 3,7,9 In our case, the initial US showed multiple hypoechoic solid thyroid nodules, similar to those seen in nodular SAT. 8 In the early stage of AG, amyloid deposition and follicular destruction with secondary fibrosis could result in multiple pseudonodules.…”

“…6 Recently, Lee et al reported a case of AG with painful goiter and transient thyrotoxicosis that was misrecognized as SAT. 7 The present case also had SAT-like clinical findings, including anterior neck pain, fever, and an elevated ESR. Previous investigators have suggested that tenderness of the thyroid gland might be caused by capsular stretching when the thyroid enlarges rapidly 6 or by destructive thyroiditis when amyloid deposition causes ischemia or mechanical pressure.…”

“…[2][3][4][5] To date, a few case reports of AG with STLS have been published. [5][6][7] In 1988, Ikenoue et al first used the term "STLS" to describe a clinical state resembling SAT in patients with AG. 5 Subsequently, Nagai et al reported on a patient with hypersensitivity vasculitis in whom AG presented as a STLS.…”

“…[1][2][3][4] The amyloid deposition is often accompanied with fatty metaplasia, so the imaging findings of AG depend on the extent of amyloid and fat deposition. 3 A few case reports of AG with clinically subacute thyroiditis (SAT)like syndrome (STLS) have been published, [5][6][7] suggesting that when patients with STLS have an unusual course or progression, the possibility of AG should be considered. [5][6][7] However, to the best of our knowledge, there has been no case report describing in detail the clinical findings and imaging features of AG mimicking SAT.…”

“…3 A few case reports of AG with clinically subacute thyroiditis (SAT)like syndrome (STLS) have been published, [5][6][7] suggesting that when patients with STLS have an unusual course or progression, the possibility of AG should be considered. [5][6][7] However, to the best of our knowledge, there has been no case report describing in detail the clinical findings and imaging features of AG mimicking SAT. Here, we present a case with detailed preoperative ultrasonography (US) and computed tomography (CT) findings along with the corresponding histopathologic features.…”