V122I TTR Cardiac Amyloidosis in Patients of African Descent: Recognizing a Missed Disease or the Dog That Didn't Bark?

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> Gregory: “Is there any other point to which you would wish to draw my attention?” > > Holmes: “To the curious incident of the dog in the night-time.” > > Gregory: “The dog did nothing in the night-time.” > > Holmes: “That was the curious incident.” > > —Arthur Conan Doyle, “Silver Blaze” in The Memoirs of Sherlock Holmes Cardiac amyloidosis is caused by the aggregation and deposition of misfolded proteins in the extracellular space of the myocardium. The heart is one of multiple organs that may be involved in systemic amyloidosis and is usually the main cause of significant morbidity and mortality. Transthyretin amyloidosis (ATTR), one of the most common forms of cardiac amyloidosis, is increasingly recognized as an important cause of heart failure with preserved ejection fraction.1 It is generally believed that for heart failure to occur, the severity of amyloid deposition in a diseased heart has to be great enough to cause abnormal wall thickening, which is easily identifiable by echocardiography. See Article by Dungu et al ATTR is caused either by wild-type transthyretin (TTR), a disease limited to the heart and predominantly of elderly males, or by mutant TTR, a disease with autosomal dominant inheritance, which may cause an isolated cardiomyopathy, isolated neuropathy, or combined disease. Numerous variants of TTR have been identified, among which is the substitution of isoleucine for valine at position 122 (V122I). This mutation has a prevalence of 3.4% in the North American population of African descent and is generally recognized as causing an infiltrative–restrictive cardiomyopathy, usually in the seventh decade and above.2 In this issue of Circulation: Heart Failure , Dungu et al3 provide data that further substantiate the importance of the V122I allele as a cause of heart failure in …