Familial Transthyretin Amyloidosis

Familial transthyretin amyloidosis is a predominant cardiac affectation that results from the infiltration into the myocardium of abnormal amyloid protein.

Prevalence is unknown.

Patients present it during adulthood (usually after age 30) with restrictive cardiomyopathy (with varying degrees of heart failure and the possibility of brady / tachyarrhythmias). Familial transthyretin amyloidosis is often accompanied by autonomic / motor and sensory polyneuropathy (familial amyloid polyneuropathy) but in some cases the phenotypic expression of familial transthyretin amyloidosis can be exclusively cardiac.

Familial transthyretin amyloidosis is transmitted as an autosomal dominant trait and to date has reported about 80 pathogenic mutations in the TTR gene (18q12.1). The phenotype of familial transthyretin amyloidosis varies depending on the particular TTR mutation, geographic area and type of aggregation (endemic/non-endemic).

The reference method for the diagnosis of amyloidosis is histological analysis and Congo red staining of biopsy specimens. The detection of mutations in TTR can confirm the diagnosis.

Many suspicious diagnoses of cardiac amyloidosis can be generated by echocardiographic characteristics and ECG findings, and can be confirmed with magnetic resonance imaging with delayed enhancement. A family history of neurological and/or cardiac disease may suggest TTR etiology.

The differential diagnosis may include other infiltrative/storage myocardial diseases, including other types of cardiac amyloidosis as AL amyloidosis; on the other hand also it is considered in the differential diagnosis of hypertrophic cardiomyopathy.

As the abnormal protein responsible familial transthyretin amyloidosis occurs almost exclusively in the liver, the only established therapy for this disease is orthotopic liver transplantation, which provides a “surgical gene therapy” for amyloid cardiomyopathy patients. Combined heart-liver transplant may also be considered. In patients with cardiac related symptoms, the percentage of patients surviving under 5 is less than 50%. The main complications are progressive heart failure and sudden death due to arrhythmia.

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