Localized Immunoglobulin Light-Chain Amyloidosis of the Ulnar Nerve

Abstract

Amyloidosis is a disorder caused by extracellular tissue deposition of insoluble fibrils. Amyloidosis can be divided into systemic or localized disease. Primary systemic amyloidosis is a multisystem disease caused by the deposition of amyloid in various tissues. Localized amyloidosis has different characteristics than those of systemic amyloidosis. In this paper, we present the case of a middle-aged woman who presented with worsening ulnar nerve palsy. Electrophysiological examination and MRI indicated a tumor surrounding the ulnar nerve in the forearm. However, the operative findings revealed that ulnar nerve fascicles were replaced with a yellow tissue, which was diagnosed as amyloid light-chain λ amyloidosis, based on histopathological examination. Systemic amyloidosis was ruled out after the screening examinations. This paper is the first report of the ulnar nerve as the sole site of localized immunoglobulin light-chain amyloidosis manifestation.

Keywords: Amyloid; Neuropathy; Ulnar nerve.

Fig. 1

The macroscopic view of the right forearm shows swelling in the medial proximal forearm on the marked area with black dots (arrow).

Fig. 2

MRI of the right forearm shows (a) the ulnar nerve is swollen with a low-signal intensity on T1-weighted images and (b) heterogeneously high-signal intensity on Gd-enhanced T1-weighted images in the sagittal view. The axial view shows flow voids (arrow) (c). Gd, gadolinium.

Fig. 3

The macroscopic view of the ulnar nerve. The right side is the proximal part. a The central part is swollen and the nerve fascicles are spread with slight hemorrhaging. b The nerve fascicles are degenerated and replaced with a yellow tissue. c The resected tissue.

Fig. 4

Histological examination. H&E staining shows that the tissue includes degenerated tissue such and bone, chondroid tissue, and hair with no remaining intact nerve fibers. The overview image (the bar = 2,000 μm) (a) and the close-up image (the bar = 100 μm) (b). c Congo red stain appears apple-green under polarized light, which suggests the diagnosis of amyloid neuropathy (the bar = 2,000 μm). d Immunohistochemical staining shows that the deposit is immunopositive for light-chain λ antibody (the bar = 500 μm). H&E, hematoxylin and eosin.