1. Dermatomyositis and polymyositis
By: Brittni McClellan

2. Classifications Dermatomyositis Polymyositis
Perimysial Inflammation and Atrophy
Endomysial Inflammation and Atrophy
CD4 Lymphocytes
CD8 Lymphocytes
perimysium is closer to the skin and therefore has cutaneous manifestations – “dermato”
endomysium is farther from the skin and therefore has no cutaneous manifestations

3. Polymyositis/dermatomyositis - description
Inflammatory Myopathy (Myositis)
Symmetric proximal muscle weakness and rash
Number of Conditions in which muscle becomes damaged by non-suppurative lymphocytic inflammatory process.
Pathophysiology:
Autoimmune
Genetics:
HLA-DQ0301
Etiology: Unknown

4. Polymyositis/dermatomyositis - description
Pathophysiology:
Focal Infiltration of T-Cells
Dermatomyositis: Perimysial
Polymyositis: Endomysial
Small number of macrophages
Muscle fiber degeneration and atrophy

5. Polymyositis/dermatomyositis – H&P
Patient History:
Diagnosis: Rash + 3 Additional Criteria
Fever
Progressive, Symmetric Weakness of Proximal Muscles
Dermatitis:
Anorexia/Weight Loss
Heliotrope Rash over Eyelids
Fatigue
Gottron Papules over Extensor Surfaces of Joints
Dysphonia
Elevated Muscle Enzymes
Weakness
EMG: Myopathy and Denervation
Difficulty Rising from Floor
Biopsy: Inflammatory Myositis
Difficulty Climbing Stairs
Difficulty Swallowing/Regurgitation through Nose
Physical Exam:
Rash (Dermatomyositis)
Above Symptoms
Nailfold Telangiectasia
Straight Leg Raise <20s

6. Polymyositis/dermatomyositis - Diagnosis
Imaging:
MRI:
Inflamed Muscles – Signal Enhancement
Used to direct biopsy
Video Swallow Study
Identify Palatal or Proximal Esophageal Weakness
Pulmonary Function Tests
Evaluates Pulmonary Musculature and Interstitial Lung Disease
Diagnosis:
Autoantibodies:
Normal Rheumatoid Factor
Normal Complement
Normal dsDNA
ANA: 10-50%
PM-1: 60% of Adults, Rare in Children
Jo-1: Associated with Interstitial Lung Disease
Enzymes: Elevated in 95% of Cases
Creatinine Kinase
Aspartate Aminotransferase (AST)
Aldolase
Lactate Dehydrogenase (LDH)

7. Polymyositis/dermatomyositis – treatment
Medication +/- Radiotherapy
Prednisone
2 mg/kg/d for 1 month
Taper over months to years
IV Gamma Globulin (Rash)
Plaquinel (Rash)
Methotrexate
Cyclosporine
Mycophenolate Mofetil
Reticulocyte count increases in 3-4 days

8. Polymyositis/dermatomyositis – treatment
Associated Conditions
Interstitial lung disease
Malignancy: Strong Association with Dermatomyositis, Less with Polymyositis
Breast or Ovarian Cancer
Prostate Cancer
Lung Cancer
Other Connective Tissue Diseases