We present a 25-year-old woman with amyloid goiter due to hypersensitivity 
vasculitis, who developed transient thyrotoxicosis resembling subacute 
thyroiditis. She received prednisolone (20 mg/ day) for three years for 
hypersensitivity vasculitis, and was diagnosed as having secondary amyloidosis 
by biopsies of the stomach, rectum and kidneys. She noticed neck swelling with 
severe right neck tenderness, palpitation, hyperhidrosis and weight loss. An 
elastic firm diffuse goiter was palpable, and the upper pole of the right lobe 
was extremely tender. Her serum free T4 and T3 levels were high, and the serum 
TSH was suppressed to subnormal. She was positive for serum C-reactive protein. 
Anti-thyroidal autoantibodies were all negative. Her thyrotoxicosis subsided 
spontaneously within one week. Serum titers of antibodies to various viruses 
were unchanged during the clinical course for two weeks, but she was positive 
for HLA B35. Examination of a needle-biopsy specimen of the thyroid gland showed 
extensive amyloid deposition and no evidence of subacute thyroiditis. We 
considered her transient thyrotoxicosis to be associated with amyloid goiter. 
The clinical course of this case was similar to the subacute thyroiditis-like 
syndrome, first described by Ikenoue et al. When patients with primary or 
secondary amyloidosis have symptoms and signs of subacute thyroiditis, but 
develop an unusual course, amyloid goiter should be considered.