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Health Dictionary

Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.

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Polymyositis and dermatomyositis differential diagnosis

Introduction

Overview

Overview

Polymyositis and Dermatomyositis must be differentiated from other inflammatory myopathies which cause muscle weakness and systemic symptoms.

Differentiating Polymyositis and Dermatomyositis from other Inflammatory Myopathies

Differentiating Polymyositis and Dermatomyositis from other Inflammatory Myopathies

Organ system Disease Symptoms History Physical

Examination

Diagnosis
Age of onset Muscle weakness Fever Myalgia Contractures Gait abnormality Neuropathy Atrophy Stiffness Myoglobinuria Other features Laboratory Findings Creatine Kinase Muscle Biopsy Electromyogram
Inflammatory/ Rheumatologic Dermatomyositis[1] 40s−50s
Can affect children 		Proximal + + − − − − + −
  • ↑↑
  • Perimysial mononuclear infiltrate
Polymyositis[2] > 18 years Proximal + + − − − − + −
  • N/A
  • N/A
  • ↑↑
  • Endomysial mononuclear infiltrate
  • Patchy necrosis
Inclusion body myositis[3] 50s Proximal
&
distal 		− − − − − − − −
  • N/A
  • Antibodies to cytoplasmic 5’−nucleotidase
  • ↑↑
Fibromyalgia[4] 40−50s Generalized − − − − + − − −
  • Normal
  • Normal
  • Normal
  • Normal
Polymyalgia Rheumatica[5] 50s Diffuse + + − − − − + −
  • History of joints stiffness, worse in the morning
  • Restricted shoulder motion
  • Normal
  • Normal
  • Normal
References

References

  1. ↑ Dalakas MC (1991). “Polymyositis, dermatomyositis and inclusion-body myositis”. N Engl J Med. 325 (21): 1487–98. doi:10.1056/NEJM199111213252107. PMID 1658649.
  2. ↑ Dalakas MC (1991). “Polymyositis, dermatomyositis and inclusion-body myositis”. N Engl J Med. 325 (21): 1487–98. doi:10.1056/NEJM199111213252107. PMID 1658649.
  3. ↑ Dalakas MC (1991). “Polymyositis, dermatomyositis and inclusion-body myositis”. N Engl J Med. 325 (21): 1487–98. doi:10.1056/NEJM199111213252107. PMID 1658649.
  4. ↑ Ohara N, Katada S, Yamada T, Mezaki N, Suzuki H, Suzuki A, Hanyu O, Yoneoka Y, Kawachi I, Shimohata T, Kakita A, Nishizawa M, Sone H (2016). “Fibromyalgia in a Patient with Cushing’s Disease Accompanied by Central Hypothyroidism”. Intern. Med. 55 (21): 3185–3190. doi:10.2169/internalmedicine.55.5926. PMC 5140872. PMID 27803417.
  5. ↑ Myklebust G, Gran JT (1996). “A prospective study of 287 patients with polymyalgia rheumatica and temporal arteritis: clinical and laboratory manifestations at onset of disease and at the time of diagnosis”. Br J Rheumatol. 35 (11): 1161–8. PMID 8948307.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Template:Aditya, Anmol Pitliya, M.B.B.S. M.D.[2]