Amyloid myopathy: expanding the clinical spectrum of transthyretin amyloidosis-case report and literature review

We identified two patients with transthyretin (ATTR) amyloid myopathy (one ATTR variant amyloidosis, ATTRv; one wild-type ATTR amyloidosis, ATTRwt). Myopathy was the initial manifestation in ATTRwt, whereas it followed neuropathy and cardiomyopathy in ATTRv. The ATTRwt patient showed muscular tracer uptake on Tc-99m-DPD planar scintigraphy at the time of initial diagnosis, consistent with ATTR amyloid myopathy. The ATTRv patient underwent heart transplantation because of progressive heart failure. Within the next two years, progressive myopathic symptoms and extracardiac tracer uptake on Tc-99m-DPD planar scintigraphy were documented, attributable to ATTR amyloid myopathy. Interstitial amyloid deposits were confirmed by muscle biopsy in both patients, with a particularly high amyloid burden in the adipose tissue. This case report highlights the frequent concomitant presence of cardiac ATTR amyloidosis and ATTR amyloid myopathy. ATTR amyloid myopathy may precede cardiac manifestation in ATTRwt or occur after heart transplantation in ATTRv. Due to the high diagnostic accuracy of Tc-99m-DPD scintigraphy for detecting ATTR amyloid myopathy and the emergence of novel therapeutics, it is important to increase the awareness of its presence.

Automated summary

This article describes two patients with ATTR amyloid myopathy, one with ATTR variant amyloidosis (ATTRv) and one with wild-type ATTR amyloidosis (ATTRwt). The ATTRwt patient showed muscular tracer uptake consistent with ATTR amyloid myopathy, while in the ATTRv patient, myopathy occurred after neuropathy and cardiomyopathy. Muscle biopsies confirmed the presence of interstitial amyloid deposits, particularly high in the adipose tissue. This case report highlights the frequent concomitant presence of cardiac ATTR amyloidosis and ATTR amyloid myopathy.