TTR and hereditary amyloidosis: Amyloid light chain (AL) amyloidosis, the most prevalent, is caused by excessive light chain production by abnormal proliferation of monoclonal B cells (typically plasmacytes).2,7 ATTR amyloidosis, the second most common, is caused either by an autosomal dominantly inherited point mutation of the precursor protein transthyretin (hereditary amyloidosis, ATTRv) or by a nonfamilial acquired form of normal TTR deposition (wild type amyloidosis, ATTRwt).2 Transthyretin is an acronym for the transport protein of thyroid hormone and retinol-binding protein.