This patient should undergo amyloid typing to classify his amyloidosis (for example, immunoglobulin light chain [AL], hereditary, or secondary [AA] amyloidosis). Amyloid typing can be accomplished by protein sequencing of the amyloid material from an involved biopsy specimen or by immunofluorescence or immunohistochemistry. He has an IgG κ monoclonal gammopathy, evidence of cardiac infiltration shown by diffuse myocardial thickening, and amyloid deposition seen on a fat pad aspirate; these findings suggest amyloid cardiomyopathy. The presence of an IgG κ monoclonal gammopathy suggests the possibility of AL amyloidosis. However, hereditary amyloidosis with incidental monoclonal gammopathy of undetermined significance (MGUS) must also be considered. The most common variant of hereditary cardiac amyloidosis is characterized by a Val122Ile mutation in transthyretin. It is present in 3.5% of black persons and is associated with late-onset cardiac involvement, typically after the age of 50 years, without evidence of other end-organ damage related to amyloidosis. Mass spectroscopy, which has 98% sensitivity and specificity, can be used to sequence and identify the composition of the amyloid deposits. Amyloid typing to establish the correct type of amyloidosis syndrome is absolutely critical, particularly in light of the high prevalence of MGUS, to avoid exposing a patient to inappropriate and potentially difficult therapy.

Chemotherapy and autologous hematopoietic stem cell transplantation (HSCT) are appropriate therapies for a patient with an established diagnosis of AL amyloidosis but not hereditary amyloidosis. A diagnosis of AL amyloidosis requires initiation of chemotherapy or pursuit of autologous HSCT, whereas a diagnosis of Val122Ile transthyretin-mutated amyloidosis is treated supportively. Patients with earlier onset hereditary amyloidosis characterized by more extensive or severe organ involvement would be considered for liver transplantation.

Although a transmyocardial biopsy would show evidence of amyloid deposition in the heart, this invasive procedure is unnecessary in patients with a typical clinical presentation, consistent noninvasive cardiac imaging findings, and documented amyloid deposition on biopsy from a noncardiac site, as seen in this patient.