Abstract

We present the case of a 69-year-old female with a medical history of insulin-dependent type 2 diabetes and myelodysplastic syndrome who presented for evaluation of growing, tender subcutaneous abdominal nodules which had been present for several years. Previous biopsy of the area was interpreted as chronic fibrosing medium-vessel vasculitis; however, the patient did not show clinical or laboratory evidence of systemic vasculitis or other connective tissue disease. Imaging of the area showed diffuse abnormal thickening of the skin and subcutaneous tissues of the anterior abdominal wall. Repeat incisional biopsy revealed concentric lamellar deposits of eosinophilic material within the walls of medium-sized subcutaneous blood vessels in association with a granulomatous, lymphoplasmacytic, and eosinophilic inflammatory infiltrate. Multinucleated histiocytes were noted around the deposits within vessel walls. A Congo red stain showed minimal apple-green birefringence under polarized light, and was initially regarded as negative for amyloid; however, examination with fluorescence microscopy showed prominent orange fluorescence within the deposits, consistent with amyloid angiopathy. Subsequent mass spectrometry for amyloid typing revealed kappa immunoglobulin light chain. CD-138, kappa, and lambda stains revealed a polytypic plasma cell population, and the patient was referred for further evaluation for systemic amyloidosis or underlying chronic inflammatory disorder. This case highlights the similar appearance of eosinophilic fibrin in vasculitis to the lamellar eosinophilic deposits in amyloid angiopathy, and illustrates the improved detection of amyloid when Congo red stains are viewed using fluorescence microscopy.

Financial Disclosure:
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