Autoantibodies in Myositis nect.com

Autoantibodies in Myositis

Pennsylvania Rheumatology Society Annual Meeting

September 23, 2018

Chester V. Oddis, MD Director, Myositis Center University of Pittsburgh

Disclosures

? Genentech: Clinical trial support ? Bristol Myers Squibb: Clinical trial support ? Mallinckrodt: Clinical trial support ? Octapharma: Clinical trial support

Lecture Objectives

? Discuss clinical features of myositis classification ? Discuss spectrum of autoantibodies seen in

patients with myositis

Classification of Myositis

? Adult polymyositis ? Adult dermatomyositis ? Juvenile myositis (DM >> PM) ? Malignancy-associated myositis ? Myositis in overlap with another AI disease ? Inclusion body myositis (IBM)

IIM: Diagnostic Criteria

Bohan and Peter (1975)

? Symmetric proximal muscle weakness ? Elevation of serum muscle enzymes: CK, aldolase, AST, ALT, LDH ? Myopathic electromyographic abnormalities: sharp waves,

fibrillations, polyphasic motor units, high frequency repetitive discharges ? Characteristic muscle pathology: myofiber degeneration/regeneration, MNC infiltrates, perifascicular atrophy ? Cutaneous features (heliotrope, Gottron sign/papules)

IIM: Diagnostic Criteria

Bohan and Peter (1975) ? Symmetric proximal muscle weakness ? Elevation of serum muscle enzymes: CK, aldolase, AST, ALT, LDH ? Myopathic electromyographic abnormalities: sharp waves,

fibrillations, polyphasic motor units, high frequency repetitive discharges ? Characteristic muscle pathology: myofiber degeneration/regeneration, MNC infiltrates, perifascicular atrophy ? Cutaneous features (heliotrope, Gottron sign/papules)

Problems with B&P Criteria ? No good way to exclude other myopathies ? Misclassification of IBM as PM ? Each criterion not explicitly defined

Lundberg et al, Ann RD, 2018

? Candidate variables assembled from published criteria/expert opinion

? Data collected from rheum/derm/neuro/peds clinics worldwide

? New criteria were derived and each item was assigned a `weighted' score

? Total score corresponds to a probability of having IIM

Lundberg et al, Ann RD, 2018

Lundberg et al, Ann RD, 2018

? For patients without classic DM rashes, do a muscle biopsy.

? For DM patients without muscle involvement do a skin biopsy.

? These criteria provide a score and probability for having IIM (for clinical trial purposes)

Rashes of DDeerrmmaattoommyyoossiittiiss Rashes

Classification of Myositis

? Adult polymyositis ? Adult dermatomyositis ? Juvenile myositis (DM >> PM) ? Malignancy-associated myositis ? Myositis in overlap with another AI disease ? Inclusion body myositis (IBM)

Classification of Myositis

? Adult polymyositis ? Adult dermatomyositis ? Juvenile myositis (DM >> PM) ? Malignancy-associated myositis ? Myositis in overlap with another AI disease ? Inclusion body myositis (IBM)

Polymyositis Mimics

? Endocrine myopathies

hyper/hypothyroid

? Drug or toxic myopathies ? Metabolic myopathies ? Mitochondrial myopathies ? Muscular dystrophies ? Infectious myositis ? Neuropathies/neurologic syndromes ? Paraneoplastic syndromes ? Other connective tissue disorders ? Miscellaneous

amyloid, sarcoid

Muscle Biopsy is a Must in "Polymyositis "

(unlike classic DM)

Muscle Biopsy is a Must in "Polymyositis "

(unlike classic DM)

And maybe pathologic classification may even be better

than "clinical" classification

Pathologic Myositis Classification

Pestronk, Curr Opin Rheum, 2011

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