A Gluteus Medius Muscle Biopsy to Confirm Amyloid Transthyretin Deposition in Wild-type Transthyretin Cardiac Amyloidosis: A Report of Two Cases.

In patients with wild-type transthyretin cardiac amyloidosis (ATTRwt-CA), the uptake of the tracer on technetium-99m-labeled pyrophosphate (Tc-PYP) scintigraphy, which indicates amyloid transthyretin (ATTR) per se, is often observed in skeletal muscles, such as the abdominal oblique and gluteal muscles. Among extracardiac biopsies for confirming ATTR deposition in ATTRwt-CA, a Tc-PYP imaging-based computed tomography (CT)-guided core needle biopsy of the internal oblique muscle has relatively high sensitivity. In some patients, the Tc-PYP uptake is more pronounced in the gluteal muscles than in oblique muscles. We herein report two cases of ATTRwt-CA in which a CT-guided biopsy of the gluteus medius muscle with Tc-PYP uptake confirmed the presence of ATTR deposits.