Transthyretin amyloidosis: Putting myopathy on the map

Introduction: Although peripheral neuropathy and cardiomyopathy are well-recognized manifestations of transthyretin (ATTR) amyloidosis, myopathy has been rarely reported. Methods: In this study we reviewed our muscle biopsy database (January 1998 to June 2018) to identify patients with ATTR amyloid myopathy confirmed by molecular or proteomic analysis. Clinical and laboratory findings were reviewed. Results: We identified eight ATTR amyloid myopathy patients (5 hereditary ATTR [ATTRv] and 3 wild-type ATTR [ATTRwt]). Myopathy was the initial manifestation in all ATTRwt patients and followed peripheral neuropathy (4 patients) or cardiomyopathy (1 patient) in ATTRv patients. One ATTRv patient developed myopathy after liver transplant. Peripheral neuropathy and cardiac amyloidosis occurred in seven and six patients, respectively. Muscle biopsy showed interstitial amyloid deposition in all patients, rare necrotic/regenerating fibers in six, and vacuoles in four. Discussion: Myopathy can be the initial manifestation of ATTRwt amyloidosis and can precede the peripheral neuropathy or occur after liver transplant in ATTRv amyloidosis.