Amyloid neuropathy: a retrospective study of 35 peripheral nerve biopsies
ABSTRACT We performed a retrospective study of 35 peripheral nerve biopsies (PNBs) with amyloid deposits in the endoneurium. In every case, nerve lesions were studied on paraffin-embedded fragments (PEFs) and by ultrastructural examination (USE). In addition, muscle fragments were taken and embedded in paraffin. Immunohistochemistry was performed with anti-transthyretin (TTR) serum on 19 nerve and 15 muscle PEFs. Direct immunofluorescence with anti-light-chain sera was performed on frozen nerve fragments in 19 cases. Endoneurial amyloid deposits were easily identified on routine PEF in 26 cases, after Congo red or thioflavine staining in three, and by USE in six. A dramatic myelinated fiber loss was evidenced in 34 cases (77-2970 per mm2), and features of axonal degeneration were present in every case. Segmental demyelination was observed in 10 cases. A mutation in the TTR gene was present in 14 cases, with Met30 mutation in 10 and Ala49 in four members of the same family. Amyloid deposits were strongly marked by the anti-TTR serum in 11 other cases, twice in the endoneurium, five around muscle fibers, and four in both locations. In eight patients, light-chain positivity was evidenced in endoneurial deposits, lambda in six and kappa in two. Two other patients with monoclonal gammopathy did not present any light-chain fixation. In 17 cases, amyloidosis was disclosed by PNB and 13 had a TTR pathology; eight of them, over 65 years old, correspond to a late-onset form of familial amyloid polyneuropathy which is an underdiagnosed condition.
Amyloid: the international journal of experimental and clinical investigation: the official journal of the International Society of Amyloidosis 08/2011; 18(Suppl. 1). DOI:10.3109/13506129.2011.574354039 · 2.51 Impact Factor
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ABSTRACT: Introduction: Acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which this occurs have not been established. Threshold tracking techniques allow in vivo assessment of the properties of the axonal membrane and may shed light on pathogenetic mechanisms underlying neuropathic disorders. Methods: We studied 10 subjects with primary amyloidosis using conventional nerve conduction studies and quantitative sensory, autonomic, and axonal excitability testing of median motor and sensory fibers. Results: As expected, subjects with amyloidosis had evidence of small- and large-fiber neuropathy on conventional testing. There was no significant difference in axonal excitability between subjects and controls apart from the stimulus required to activate sensory fibers. Discussion: Amyloid-related neuropathy does not involve a change in membrane potential as either a primary or secondary event. This suggests that ischemia and axonal compression are unlikely mechanisms for the neuropathy. © 2014 Wiley Periodicals, Inc.Muscle & Nerve 11/2014; 51(3). DOI:10.1002/mus.24508 · 2.31 Impact Factor
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ABSTRACT: Simultaneous combined superficial peroneal nerve and peroneous brevis muscle biopsy, via the same cutaneous incision, allows examination of several tissue specimens and significantly improves the diagnosis of systemic diseases with peripheral nerve involvement. Vasculitides are certainly the most frequently diagnosed on neuro-muscular biopsies, but this procedure is also well advised to asses a diagnosis of sarcoidosis or amyloidosis. More occasionally, combined nerve and muscle biopsy may reveal an unpredicted diagnosis of cholesterol embolism, intra-vascular lymphoma, or enables complementary diagnosis investigations on mitochondrial cytopathy or storage disease.Clinical neuropathology 03/2014; 33(05). DOI:10.5414/NP300740 · 1.31 Impact Factor