Glu89Gln transthyretin-related amyloidosis in Italy and Bulgaria: does geographic area influence phenotype beyond the shared mutation?

Background Glu89Gln transthyretin (TTR) variant is a well-known cause of systemic amyloidosis with a cardiologic, neurologic or mixed phenotype. Even though Glu89Gln transthyretin (TTR) variant has been described worldwide, it remains unknown whether geographical area influences the phenotypic expression of the disease (as happens with the Val30Met mutation, which is known to manifest with different phenotypes in different geographical contexts). We hypothesized that significant phenotypic differences exist between patients with Glu89Gln-related amyloidosis according to the specific geographic origin.