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Case Reports in Hematology
Volume 2018, Article ID 9840405, 5 pages
https://doi.org/10.1155/2018/9840405
Case Report

A Rare Case of Systemic AL Amyloidosis with Muscle Involvement: A Misleading Diagnosis

1UO di Ematologia e CTMO, Azienda Ospedaliero-Universitaria di Parma and Department of Medicine and Surgery, University of Parma, Parma, Italy
2Department of Biomedical and Neuromotor Sciences, Alma Mater University of Bologna, Bologna, Italy
3Muscle and Nerve Histopathology Laboratory, Neurology Unit, Azienda Ospedaliero-Universitaria di Parma, University of Parma, Parma, Italy
4Department of Diagnostic Medicine, Electron Microscopy Laboratory, IRCCS Fondazione Policlinico San Matteo and University of Pavia, Pavia, Italy
5Pathology Unit, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy

Correspondence should be addressed to Nicola Giuliani; ti.rpinu@inailuig.alocin

Received 24 July 2017; Accepted 27 December 2017; Published 31 January 2018

Academic Editor: Uma Dasgupta

Copyright © 2018 Fabrizio Accardi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Muscle involvement in AL amyloidosis is a rare condition, and the diagnosis of amyloid myopathy is often delayed and underdiagnosed. Amyloid myopathy may be the initial manifestation and may precede the diagnosis of systemic AL amyloidosis. Here, we report the case of a 73-year-old man who was referred to our center for a monoclonal gammopathy of undetermined significance (MGUS) diagnosed since 1999. He reported a progressive weakness of proximal muscles of the legs with onset six months previously. Muscle biopsy showed mild histopathology featuring alterations of nonspecific type with a mixed myopathic and neurogenic involvement, and the diagnostic turning point was the demonstration of characteristic green birefringence under cross-polarized light following Congo red staining of perimysial vessels. Transmission electron microscopy (TEM) confirmed amyloid fibrils around perimysial vessels associated with collagen fibrils. A stepwise approach to diagnosis and staging of this disorder is critical and involves confirmation of amyloid deposition, identification of the fibril type, assessment of underlying amyloidogenic disorder, and evaluation of the extent and severity of amyloidotic organ involvement.