Amyloid inflammatory myopathy: report of two cases and literature review (P9-8.009)

Abstract

<h3>Objective:</h3> Our review of the literature revealed a few reported cases of amyloid myopathy (AM) associated with mild to moderate infiltration of inflammatory cells. <h3>Background:</h3> AM is a clinically and etiologically heterogenous group of myopathies. It is rarely associated with myositis, although there have been occasional reports of AM masquerading idiopathic inflammatory myopathies (IIMs) such as polymyositis and inclusion body myositis. Pathologically, AM is characterized by amyloid deposits in the intramuscular blood vessels or connective tissue elements, and reportedly not in myofibers. <h3>Design/Methods:</h3> We present two cases of AM with inflammatory myopathy (IM) features. <h3>Results:</h3> <h3>Case 1:</h3> 62-year-old male with a 1-year history of dilated cardiomyopathy presented with significant proximal muscle weakness. His serum creatine kinase (CK) levels were moderately elevated. A right deltoid muscle biopsy demonstrated myopathic changes with necrotic fibers, many CD68+ macrophages, occasional CD8+ T-cells, MHC-1 sarcolemmal/sarcoplasmic positivity, and amyloid deposits in the intramuscular blood vessels. A subsequent bone marrow biopsy revealed the IGH-CCND1 rearrangement with malignant 25% lambda light-chain restricted plasma cells. <h3>Case 2:</h3> 58-year-old female presented with generalized weakness, lower extremity edema, decreased exercise tolerance and lethargy over 4 weeks. She was recently diagnosed with kappa light-chain multiple myeloma by a bone marrow biopsy showing 80% kappa light-chain restricted plasma cells. Despite normal CK while receiving dexamethasone, the thigh muscle magnetic resonance imaging and clinical features were consistent with IM. A left thigh muscle biopsy demonstrated myopathic changes including necrotic fibers and amyloid deposits in the necrotic fibers, endomysial/perimysial tissue, and blood vessels. It also revealed abundant inflammatory cell infiltrates including CD68+ macrophages, CD8+ T-cells, and CD20+ B-cells with MHC-1 sarcolemmal/sarcoplasmic positivity. <h3>Conclusions:</h3> Our cases and literature review suggest that AM may present with IM features including unusual features such as B-cell inflammatory foci. IM associated with AM (amyloid IM) may be secondary or a subtype of IIMs. <b>Disclosure:</b> Dr. Gupta has nothing to disclose. Dr. Bhavsar has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Pfizer. Dr. Bhavsar has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Abbvie. Dr. Bhavsar has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB. Dr. Bhavsar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Novartis. Dr. Fareez has nothing to disclose. Dr. Tarnopolsky has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Sanofi-Genzyme. Dr. Tarnopolsky has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Reneo. Dr. Tarnopolsky has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Alexion. Dr. Tarnopolsky has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Reneo . Dr. Tarnopolsky has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Sanofi-Genzyme. Dr. Tarnopolsky has stock in Synaptive Medical. Dr. Tarnopolsky has stock in CloudDx. The institution of Dr. Tarnopolsky has received research support from Canadian Institute for Health Research. Dr. Tarnopolsky has received intellectual property interests from a discovery or technology relating to health care. Dr. Lu has nothing to disclose.