Abstract Details

Title Myopathy: An Underrecognized Presentation of Transthyretin Amyloidosis

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) S42 - Neuromuscular Disorders (4:14 PM-4:25 PM)

Poster/Presentation
Number 005

Background Transthyretin amyloidosis (ATTR) is a multi-system disorder characterized by deposition of amyloid fibrils derived from either mutated transthyretin (hereditary ATTR or hATTR) or non-mutated transthyretin (wild-type ATTR or wtATTR). While peripheral neuropathy and cardiomyopathy are known common manifestations of ATTR, myopathy has been rarely reported.

Objective To characterize transthyretin amyloid myopathy

Design/Methods We reviewed our muscle biopsy database (January 1998-June 2018) to identify patients with amyloid myopathy. We included only patients with ATTR amyloid myopathy confirmed by molecular or proteomic analysis. Clinical, electrophysiological and laboratory data were reviewed.

Results We identified 8 patients with ATTR amyloid myopathy (5 hATTR and 3 wtATTR). Median age at diagnosis was 66 years (range 45-83). Median time from myopathy onset-to-diagnosis was 12.5 months (range 1-420) Myopathy was the first manifestation of amyloidosis and preceded other organ involvement in all 3 wtATTR patients. Conversely, the myopathy followed the peripheral neuropathy by 4-100 months in 4 patients, and the cardiomyopathy by 12 months but was not the peripheral neuropathy in 1 patient) in the hATTR group. One hATTR patient developed myopathy 3 years after liver transplant. The weakness was proximal predominant (n=4), distal predominant (n=1) and proximodistal (n=3) , and accompanied by distal sensory deficits in 7 patients. Creatine kinase (CK) was elevated in 3 patients (358-610 U/L), all of whom had cardiomyopathy. EMG revealed myopathic changes in proximal and axial muscles in all, but one patient. Only 1 patient had fibrillation potentials in myopathic muscles. Apart from intramuscular interstitial congophilic deposits, muscle biopsy showed rare necrotic or regenerating fibers in 6 patients and vacuoles in 5 patients (2 rimmed, 2 non-rimmed and 1 both types) .

Conclusions ATTR amyloid myopathy can be the initial manifestation of ATTR amyloidosis andpatients may develop myopathy even after liver transplant. Concomitant peripheral neuropathy is common. HyperCKemia seems to predict coexisting amyloid cardiomyopathy.

Authors/Disclosures
Marcus Vinicius R. Pinto, MD (Mayo Clinic) PRESENTER	Dr. Pinto has nothing to disclose.
Margherita Milone, MD, FAAN (Mayo Clinic)	Dr. Milone has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. Dr. Milone has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology Genetics, AAN. The institution of Dr. Milone has received research support from Mayo Clinic, CCaTS-CBD. The institution of Dr. Milone has received research support from Mayo Clinic, SGP Award. The institution of Dr. Milone has received research support from MDA for Care Center grant. The institution of Dr. Milone has received research support from Regenerative medicine Minnesota.
Michelle L. Mauermann, MD, FAAN (Mayo Clinic)	The institution of Dr. Mauermann has received research support from IONIS. The institution of Dr. Mauermann has received research support from Alnylam. Dr. Mauermann has received publishing royalties from a publication relating to health care.
Reem M. Alhammad, MD (King Saud University)	No disclosure on file
	No disclosure on file
Teerin Liewluck, MD, FAAN (Department of Neurology, Mayo Clinic)	Dr. Liewluck has nothing to disclose.

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