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Abstract Details

Inclusion Body Myositis: Correlation of Clinical Outcomes with Histopathological, Electromyographic and Laboratory Findings
Neuromuscular and Clinical Neurophysiology (EMG)
Neuromuscular and Clinical Neurophysiology (EMG) Posters (7:00 AM-5:00 PM)
109
To determine which histopathological, electromyographic and laboratory markers correlate with clinical outcomes in Inclusion Body Myositis (IBM).
IBM pathogenesis is not fully elucidated, and consists of an interplay between inflammatory and neurodegenerative pathways. Available outcome measures are scarce.
We reviewed our database to identify patients with IBM according to ENMC 2011 criteria, seen between 2015 and 2020. We only included patients who had a muscle biopsy and EMG performed on the same muscle (opposite or same side). We used a detailed grading system ranging from 0- normal to 4- severe to grade histopathological findings in each biopsy. EMG findings were graded from 0 to 4 according to the standard protocol in our EMG laboratory. Clinical severity was reflected by the modified Rankin scale, muscle strength sum score, and strength of biopsied/needled muscle. Serum markers of interest were creatine kinase level, and cN-1A antibodies. 

50 patients were included, with a median age at presentation of 69 years. 64% were males. Median disease duration at diagnosis was 51 months. 20/30 patients had positive cN-1A antibodies. There was a strong correlation among the various clinical outcome measures, and with disease duration. On muscle biopsy, endomysial inflammation and the degree of auto-aggressive features were the main correlates for clinical severity, whereas vacuoles and congophilic inclusions did not correlate with outcomes. On EMG, the degree of shortness of the motor unit potentials’ duration strongly correlated with disease severity. Myotonic discharges correlated with the severity of inflammation. Fibrillation potentials correlated with a variety of histopathological findings and CK level. None of the serum markers correlated with any of the clinical outcomes.

Endomysial inflammation is the main correlate of clinical severity in IBM on muscle biopsy. Establishing standardized quantitative methods for motor unit analysis on EMG may serve as a clinical outcome measure in IBM.

Authors/Disclosures
Marcus Vinicius R. Pinto, MD (Mayo Clinic)
PRESENTER 		Dr. Pinto has nothing to disclose.
Elie Naddaf, MD (Mayo Clinic) Dr. Naddaf has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Expert Connect. Dr. Naddaf has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Klick, Inc. Dr. Naddaf has received personal compensation in the range of $500-$4,999 for serving as a Consultant for WebMD. Dr. Naddaf has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Johnson and Johnson. Dr. Naddaf has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Arcellx. The institution of Dr. Naddaf has received research support from NIAMS. The institution of Dr. Naddaf has received research support from Fulcrum therapeutics. The institution of Dr. Naddaf has received research support from Abcuro. The institution of Dr. Naddaf has received research support from Cabaletta . The institution of Dr. Naddaf has received research support from Arcellx.