Diagnosis and Therapeutic Approaches to Transthyretin Amyloidosis

Hereditary amyloidogenic transthyretin (TTR) (ATTR) amyloidosis is an autosomal dominant form of fatal hereditary amyloidosis. Owing to progress in biochemical and molecular genetic analyses, this disease is now believed to occur worldwide. As of today, reports of about 120 different points of single or double mutations, or a deletion in the TTR gene have been reported, and several different phenotypes of ATTR amyloidosis have been documented. In addition, since liver transplantation has been established to halt the progression of hereditary ATTR amyloidosis in the early stage, rapid and reliable diagnostic system for ATTR amyloidosis is needed. On the other hand, senile systemic amyloidosis (SSA) derived from wild-type (WT) TTR affects primarily in the heart and lungs and occasionally in carpal ligaments in the elderly. To perform accurate diagnosis and effective treatments, we should distinguish between hereditary ATTR amyloidosis and SSA by means of genetic and proteomic analyses. The liver transplantation for hereditary ATTR amyloidosis has become a well-established treatment, because the main source of serum variant TTR is shut out. However, this treatment has several problems, such as expensive medical costs, lifelong administration of immunosuppressants, non-indication for the mutated-TTR gene carriers without clinical symptoms, shortage of liver donors, and further development of cardiac and ocular disorders. Therefore, we and other ATTR amyloidosis research groups have been investigating the possibility of stabilization of variant TTR, gene therapy, and immunotherapy for ATTR amyloidosis on the basis of TTR amyloid formation mechanism. We present here the current diagnostic procedure and therapeutic approaches for the disease.