Variant transthyretin amyloid cardiomyopathy (ATTRv-CM) is a rare disease caused by a genetic mutation in the ATTR gene. Due to the pathogenic mutation, transthyretin tetramers lose their structural stability and misfold, leading to the accumulation of amyloid fibrils in various tissues, particularly in the heart. The clinical progression of ATTRv-CM varies depending on the specific mutation. Data on ATTR gene mutations in Türkiye are limited. This paper presents a case of spontaneous biceps tendon rupture, identified prior to diagnosis, in a patient with ATTRv-CM carrying a heterozygous c148G>A pVal50Leu mutation.