Application of Electrical Impedance Myography (EIM) as a Potential Biomarker of Idiopathic Inflammatory Myopathies

Application of Electrical Impedance Myography (EIM) to Establish Muscle Impedance Parameters as a Potential Biomarker of Idiopathic Inflammatory Myopathies (IIMs)

1. To assess changes in impedance parameters in Idiopathic Inflammatory Myopathies (IIMs).
2. To assess whether EIM parameters are reflective of disease severity, based on clinical outcome measures of IIMs.

1. To assess changes in impedance parameters in Idiopathic Inflammatory Myopathies (IIMs) There are structural and compositional changes in muscles, such as edema, adipose infiltration, and/or atrophy, in IIMs. Electrical impedance myography (EIM) is sensitive to such changes. EIM parameters will be different when compared to healthy controls in IIMs.
2. To assess whether EIM parameters are reflective of disease severity, based on clinical outcome measures of IIMs.

Clinical outcome measures reflect on disease severity which is an indirect measure of muscle involvement in IIMs. If EIM parameters correlate with clinical outcome measure, it would indirectly prove that EIM can reflect disease severity in IIMs

Inclusion Criteria:

• duration of weakness >12 months.
• ages 18 to 80 years old.
• serum CK level no greater than 15 times the upper limit of normal.
• quadriceps weakness >hip flexor weakness and/or finger flexor weakness >shoulder abduction weakness.
• one or more of the following pathological findings:
• endomysial inflammatory infiltrate.
• rimmed vacuoles.
• protein accumulation or 15-18 mm filaments.

DM/PM inclusion criteria:

• ages 18 to 80
• Symmetric proximal weakness
• Elevated CK
• EMG suggestive of myopathy with evidence of muscle membrane irritation
• Muscle biopsy suggestive of inflammatory myositis (degeneration, regeneration, necrosis, and interstitial mononuclear infiltrates)
• Typical skin rashes of DM (Heliotrope rash or Gottron sign)

Key inclusion criteria for the control group:

• no active neuromuscular disorders or known history of neuromuscular disorders.
• no sign or symptoms of muscle weakness.
• no family history of muscular dystrophies or ALS.
• ages 18 to 80

Exclusion Criteria:

• Patients with decompensated congestive heart failure
• Patients with chronic kidney disease on hemodialysis
• Patients with active cancer on chemotherapy or radiotherapy
• Patients with severe disease who are already wheel chair bound