Low Prevalence of Clinically Apparent Cardiac Amyloidosis Among Carriers of Transthyretin V122I Variant in a Large Electronic Medical Record.

BACKGROUND

Transthyretin (TTR) gene mutations are the most common cause of hereditary amyloidosis. Valine replaced by isoleucine in position 122 (V122I) variant is common, particularly in the black population. Carriers of V122I have increased risk for developing cardiac amyloidosis. Despite a relatively high prevalence, the penetrance of V122I is not firmly established. This study sought to determine the prevalence of clinically apparent cardiac amyloidosis among carriers of the TTR V122I variant.

METHODS

BioVU, a Vanderbilt University resource linking DNA samples and pre-existing genetic data to de-identified electronic medical records was used to identify TTR V122I mutation carriers. Automated billing code queries (International Classification of Diseases, 9th revision codes), problem list searches, and manual chart reviews were used to identify subjects with clinically diagnosed cardiac amyloidosis.

RESULTS

Among 28,429 subjects with available genotype data, 129 were V122I carriers. Carriers had a median age of 42 years (interquartile range 16-64). Noncarriers had a median age of 62 years, (interquartile range 41-77). The carrier rate was 3.7% in blacks and 0.02% in whites. Overall, the prevalence of clinically apparent cardiac amyloidosis was 0.8% in carriers and 0.04% in noncarriers (P = .05). Above age 60, the prevalence of cardiac amyloidosis was 2.6% in carriers and 0.06% in noncarriers (P = .03).

CONCLUSION

Carriers of the TTR V122I variant are at a higher risk for development of cardiac amyloidosis, particularly at age>60 years. However, clinically apparent cardiac amyloidosis in this population was uncommon. These results support that the penetrance of TTR V122I is age dependent and suggest it may be significantly lower than previously reported.