The Rheumatologist
COVID-19 News
  • Connect with us:
  • Facebook
  • Twitter
  • LinkedIn
  • YouTube
  • Feed
  • Home
  • Conditions
    • Rheumatoid Arthritis
    • SLE (Lupus)
    • Crystal Arthritis
      • Gout Resource Center
    • Spondyloarthritis
    • Osteoarthritis
    • Soft Tissue Pain
    • Scleroderma
    • Vasculitis
    • Systemic Inflammatory Syndromes
    • Guidelines
  • Resource Centers
    • Axial Spondyloarthritis Resource Center
    • Gout Resource Center
    • Psoriatic Arthritis Resource Center
    • Rheumatoid Arthritis Resource Center
    • Systemic Lupus Erythematosus Resource Center
  • Drug Updates
    • Biologics & Biosimilars
    • DMARDs & Immunosuppressives
    • Topical Drugs
    • Analgesics
    • Safety
    • Pharma Co. News
  • Professional Topics
    • Ethics
    • Legal
    • Legislation & Advocacy
    • Career Development
      • Certification
      • Education & Training
    • Awards
    • Profiles
    • President’s Perspective
    • Rheuminations
    • Interprofessional Perspective
  • Practice Management
    • Billing/Coding
    • Quality Assurance/Improvement
    • Workforce
    • Facility
    • Patient Perspective
    • Electronic Health Records
    • Apps
    • Information Technology
    • From the College
    • Multimedia
      • Audio
      • Video
  • Resources
    • Issue Archives
    • ACR Convergence
      • Systemic Lupus Erythematosus Resource Center
      • Rheumatoid Arthritis Resource Center
      • Gout Resource Center
      • Abstracts
      • Meeting Reports
      • ACR Convergence Home
    • American College of Rheumatology
    • ACR ExamRheum
    • Research Reviews
    • ACR Journals
      • Arthritis & Rheumatology
      • Arthritis Care & Research
      • ACR Open Rheumatology
    • Rheumatology Image Library
    • Treatment Guidelines
    • Rheumatology Research Foundation
    • Events
  • About Us
    • Mission/Vision
    • Meet the Authors
    • Meet the Editors
    • Contribute to The Rheumatologist
    • Subscription
    • Contact
  • Advertise
  • Search
You are here: Home / Articles / Inflammatory Myopathies Difficult to Diagnose, Treat

Inflammatory Myopathies Difficult to Diagnose, Treat

December 1, 2013 • By Jonathan Jones, MD, and Robert Wortmann, MD

  • Tweet
  • Email
Print-Friendly Version / Save PDF

You Might Also Like
  • Myopathies
  • ACR 2013 State-of-the-Art Clinical Symposium: How to Identify Signs of Myositis and Metabolic Myopathies
  • New Approaches to Inflammatory Myopathy
Explore This Issue
December 2013
The Challenge of Inflammatory Myopathies

ad goes here:advert-1
ADVERTISEMENT
SCROLL TO CONTINUE

Rheumatologists often have varying levels of comfort in assessing and managing muscle disease. For many, these diseases are challenging because of the difficulty in accurately diagnosing myopathies and establishing effective therapeutic regimens. We outline three key issues in diagnosing and managing inflammatory myopathies.

No Gold Standard for Diagnosis

Because there is no gold standard for diagnosing idiopathic inflammatory myopathies, we are forced to rely on criteria. Although more than a dozen sets of criteria have been proposed, the first set, published in 1975 by Bohan and Peter, remains the mainstay.1,2 For the diagnosis of polymyositis, they proposed the combination of proximal muscle weakness, elevated serum levels of enzymes derived from skeletal muscle, a classic triad of electromyographic (EMG) abnormalities, and the presence of inflammation on muscle biopsy. The diagnosis of dermatomyositis could be rendered with the addition of a characteristic skin rash. These parameters seem clear cut until one gets into the details, because each criterion by itself is very nonspecific. For example, fixed proximal muscle weakness may be the hallmark of inflammatory myopathies, but this symptom may be caused by a myriad of other conditions (see Table 1).

ad goes here:advert-2
ADVERTISEMENT
SCROLL TO CONTINUE

When elevated, the enzyme most considered to be a sign of myositis is creatine phosphokinase (CPK). It is sometimes mistakenly believed that CPK must be elevated at least one time during the course of polymyositis, but this is not always the case. Some patients have normal CPK levels throughout their course. Furthermore, there are several other causes of an elevated CPK, including exercise (anaerobic and aerobic), trauma (blunt or sharp), drugs (statins, colchicine, alcohol, cocaine), and toxins. Carriers for muscular dystrophy or some metabolic myopathies may have an increased serum CPK. Healthy African-American males commonly have CPK levels above the upper limits of normal reported for the population as a whole. Finally, in large clinical trials using statin drugs, over 30% of individuals have elevated CPK levels. Interestingly, the percentage was the same for those taking placebo as it was for those taking study drugs.3 Thus, relying on this test as a way to screen for muscle inflammation can be problematic.

Causes of Proximal Muscle Weakness That May Mimic Inflammatory Myopathy
click for large version
Table 1: Causes of Proximal Muscle Weakness That May Mimic Inflammatory Myopathy

The classic triad of EMG changes described includes: 1) fibrillation at rest, increased insertional activity, and spontaneous and positive sharp waves; 2) bizarre high-frequency repetitive discharges; and 3) polyphasic potentials of short duration and low amplitude.1,2 However, this triad is not diagnostic and is generally present in only 40% of patients with myositis, while 10% of patients with these diseases have normal EMG results.4

ad goes here:advert-3
ADVERTISEMENT
SCROLL TO CONTINUE

Pages: 1 2 3 4 5 | Single Page

Filed Under: Conditions, Systemic Inflammatory Syndromes Tagged With: dermatomyositis, diagnose, inflammatory myopathy, myositis, polymyositis, rheumatology, TreatmentIssue: December 2013

You Might Also Like:
  • Myopathies
  • ACR 2013 State-of-the-Art Clinical Symposium: How to Identify Signs of Myositis and Metabolic Myopathies
  • New Approaches to Inflammatory Myopathy
  • ACR/ARHP Annual Meeting 2012: Use a Combination of Tests, Patient History, and Physical Exam when Assessing Myopathies

ACR Convergence

Don’t miss rheumatology’s premier scientific meeting for anyone involved in research or the delivery of rheumatologic care or services.

Visit the ACR Convergence site »

Meeting Abstracts

Browse and search abstracts from the ACR Convergence and ACR/ARP Annual Meetings going back to 2012.

Visit the Abstracts site »

Simple Tasks

Learn more about the ACR’s public awareness campaign and how you can get involved. Help increase visibility of rheumatic diseases and decrease the number of people left untreated.

Visit the Simple Tasks site »

The Rheumatologist newsmagazine reports on issues and trends in the management and treatment of rheumatic diseases. The Rheumatologist reaches 11,500 rheumatologists, internists, orthopedic surgeons, nurse practitioners, physician assistants, nurses, and other healthcare professionals who practice, research, or teach in the field of rheumatology.

About Us / Contact Us / Advertise / Privacy Policy / Terms of Use

  • Connect with us:
  • Facebook
  • Twitter
  • LinkedIn
  • YouTube
  • Feed

Copyright © 2006–2022 American College of Rheumatology. All rights reserved.

ISSN 1931-3268 (print)
ISSN 1931-3209 (online)