Phenotypic profile of Ile68Leu transthyretin amyloidosis: an underdiagnosed cause of heart failure

Aims: Cardiac amyloidosis remains a great challenge for the cardiologist. One of the three main aetiological forms, transthyretin-related hereditary amyloidosis (ATTRm), can present with several phenotypes, depending mainly on the specific mutation. We aimed to characterize the phenotype of patients with ATTRm due to Ile68Leu mutation, comparing them to patients with wild-type transthyretin amyloidosis (ATTRwt). Methods and results: Data of 67 Ile68Leu ATTRm patients from two Italian referral centres (Bologna and Florence) were retrospectively analysed and compared to those of 82 ATTRwt patients. Fifty-five unaffected mutation carriers were also analysed. Cumulative disease onset was 50% at age 71. A total of 56/67 (84%) patients had a predominantly cardiac phenotype at presentation with concentric increase in left ventricular wall thickness [median 17 mm], and normal or near normal left ventricular ejection fraction (79% of patients). Low QRS voltages were present only in 29% of patients but voltage/mass ratio was low (0.5). Carpal tunnel syndrome was noted in 43%. The overall phenotypic profile was similar to ATTRwt but Ile68Leu ATTRm patients typically presented younger (median 71 vs. 78 years) and were more likely to have (mild) symptomatic neurological involvement (19% vs. 2%). Male prevalence was 44% in unaffected mutation carriers and 78% in affected patients. Age-adjusted survival was comparable between groups. Conclusions: Ile68Leu ATTRm is a cause of familial amyloidotic cardiomyopathy endemic in central-northern Italy and presents as hypertrophic/restrictive cardiomyopathy quite similar to ATTRwt. Male preponderance is present in affected patients but not in unaffected mutation carriers. Age-adjusted survival is similar to ATTRwt.