A novel variant of transthyretin (Glu42Asp) associated with sporadic late-onset cardiac amyloidosis

Serum transthyretin levels in senile systemic amyloidosis: effects of age, gender and ethnicity

Serum transthyretin (TTR) levels are reduced in familial amyloidotic polyneuropathy (FAP). A single study of patients with senile systemic amyloidosis (SSA) in Sweden found that those individuals also had a significantly lower mean serum TTR concentration than age- and gender-matched controls. To determine if the same phenomenon prevailed in an ethnically more heterogeneous population, we compared the serum TTR levels, as determined by ELISA, in 45 documented SSA patients with congestive heart failure, 20 AL patients with congestive heart failure and population controls. Serum TTR concentrations in the controls were influenced in a statistically significant manner by age, gender and ethnicity. Although it is unlikely that such differences are clinically relevant, they must be considered when assessing the meaning of serum TTR concentrations in any clinically defined population. The serum concentrations in patients with SSA did not differ from age, gender and ethnically matched controls or from a group of AL patients with significant clinical cardiac involvement. We also compared TTR concentrations in 12 African-Americans carrying the TTR V122I allele with those in 826 African-Americans who were homozygous wild type at the TTR locus. The TTR V122I carriers had significantly lower serum TTR concentrations than appropriate controls even though the majority of such individuals had not reached the age of clinical or anatomic risk, i.e. over 60. Thus, as in carriers of other TTR mutations the serum TTR level is lower than normal, despite having a much later appearance of clinical disease.

Clinical and pathological studies of cardiac amyloidosis in transthyretin type familial amyloid polyneuropathy

To clarify the clinicopathological features of cardiac amyloidosis in transthyretin (TTR) familial amyloid polyneuropathy (FAP), 169 patients were divided into three groups. Group I consisted of 113 patients with ATTR Val30Met who originated from an endemic focus, II consisted of 36 patients with ATTR Val30Met in nonendemic areas, and III consisted of 20 patients who had non-Val30Met ATTRs with 15 different gene mutations. The median age of onset in Group I was 34 years. On our initial examination, only one 65-year-old female patient was found to be suffering from congestive heart failure. During the follow-up of 65 patients, 7 developed congestive heart failure, the average duration of their illness being 8.7 years. In Group II, the median age of onset was 53 years and 6 of the 36 patients were diagnosed as having cardiac amyloidosis in the course of this disease. In 20 autopsied patients with ATTR Val30Met, congestive heart failure was clinically seen in 6 of the 20 and all 6 showed considerably increased cardiac weight (500g or more). In Group III patients with non-Val30Met ATTRs, the median age of onset was 51.5 years and 14 of the 20 patients had cardiac amyloidosis with congestive heart failure on admission or soon after a definite diagnosis. Cardiac amyloidosis occurs in the classical form of FAP with ATTR Val30Met, especially in older patients, and is also a common clinical manifestation in FAP patients with non-Val30Met ATTRs. In the pathogenesis of cardiac amyloidosis in ATTR FAP, aging seems to play an important role.

Transthyretin mutations in hyperthyroxinemia and amyloid diseases

Over 80 different disease-causing mutations in transthyretin (TTR) have been reported. The vast majority are inherited in an autosomal dominant manner and are related to amyloid deposition, affecting predominantly peripheral nerve and/or the heart. A small portion of TTR mutations are apparently non-amyloidogenic. Among these are mutations responsible for hyperthyroxinemia, presenting high affinity for thyroxine (a TTR ligand). Compound heterozygotic individuals for TTR mutants have been described; noteworthy is the clinically protective effect exerted by a non-pathogenic over a pathogenic mutation. Current TTR mutations and their significance are briefly reviewed here.

Postmortem findings in two familial amyloidosis patients with transthyretin variant Asp38Ala

Postmortem findings in 2 familial amyloidosis patients with the transthyretin variant (ATTR), Asp38Ala, are described Both showed cardiac failure, and progressive peripheral and autonomic neuropathy and died at the ages 82 and 57, respectively. TTR immunoreactive amyloid deposition was observed to be extensive in the myocardium, peripheral nerves, sympathetic ganglia and gastrointestinal tract. The pulmonary parenchyma was also diffusely involved, but renal glomeruli, follicular tissues of the thyroid, and the leptomeninges and subarachnoidal vessels of the central nervous system showed little deposition. The latter findings are not usually seen in the patients with ATTR Val30Met, the most common form of familial amyloidosis. Additionally, the clinicopathological findings of familial amyloidosis with ATTR Asp38Ala seem to vary in the different individuals.

[Clinical or biological symptoms leading to the search for amyloidosis]

INTRODUCTION

The extracellular, multifocal, disseminated or diffuse localization of amyloidosis accounts for the diversity of clinical presentations and late diagnosis.

CURRENT KNOWLEDGE AND KEY POINTS

However, early diagnosis is important, as new drugs have been recently introduced. Both clinical picture and biology help guide diagnosis, including either kidney, heart, skin or neurologic involvement associated with monoclonal gammapathy (primary idiopathic amyloidosis AL); underlying inflammatory or infectious disease, familial Mediterranean fever with proteinuria (secondary amyloidosis AA); cardiac, neurologic or ocular involvement (heredofamilial amyloidosis); carpal tunnel syndrome, joint pain (amyloidosis of hemodialysis). Furthermore, amyloid fibrils are identified on salivary gland biopsy.

FUTURE PROSPECTS AND PROJECTS

Due to the introduction of new specific drugs aimed at curing various amyloidoses, early diagnosis is important. Chemotherapy and hematopoietic stem cell transplantation are promising regarding AL amyloidosis, while liver transplantation has proven remarkably successful in heredofamilial amyloidosis. Progress in molecular biology should allow identification of various forms of familial amyloidosis.