Hereditary Transthyretin Amyloidosis (Hattr) is an important component in the neurobiology of neurodegenerative . This page provides detailed information about its structure, function, and role in disease processes.
Hereditary transthyretin amyloidosis (hATTR) is a progressive, systemic, and ultimately fatal protein misfolding disease caused by autosomal dominant mutations in the TTR gene [1]
encoding transthyretin. The disease is characterized by the extracellular deposition of amyloid fibrils composed of misfolded transthyretin protein in multiple organs, most [2]
commonly the peripheral nerves, autonomic nervous system, heart, kidneys, and gastrointestinal tract. hATTR represents one of the most important hereditary systemic amyloidoses and [3]
serves as a paradigmatic model for understanding protein aggregation and misfolding in human disease [4]. [5]
The disease was first described by Corino de Andrade in 1952 in families from northern Portugal, where the Val30Met mutation remains endemic. Since then, over 140 pathogenic TTR mutations have been identified worldwide, establishing hATTR as a genetically heterogeneous condition with remarkable phenotypic variability. The global prevalence is estimated at approximately 50,000 individuals, though the disease is significantly underdiagnosed, particularly in non-endemic regions. [6]
Transthyretin (TTR) is a 55-kDa homotetrameric protein primarily synthesized in the liver, choroid plexus, and retinal pigment epithelium. Under physiological conditions, TTR circulates as a stable tetramer in the plasma and cerebrospinal fluid, where it serves as a transport protein for thyroxine (T4) and retinol-binding protein–retinol complex (vitamin A). The tetrameric structure is critical for TTR stability and function, with each monomer consisting of 127 amino acid residues arranged in a beta-sheet-rich structure [2:1]. [7]
The pathogenesis of hATTR involves a cascade of molecular events beginning with destabilization of the TTR tetramer: [8]
The amyloidogenic process in hATTR shares mechanistic parallels with amyloid in alzheimers and alpha-synuclein aggregation in parkinsons, underscoring conserved principles of protein misfolding across neurodegenerative [3:1]. [9]
Peripheral nerve injury in hATTR polyneuropathy results from multiple pathological : [10]
Over 140 amyloidogenic TTR mutations have been identified, with significant genotype-phenotype correlations: [11]
| Mutation | Phenotype | Endemic Region | Onset | [12]
|----------|-----------|----------------|-------|
| Val30Met (V30M) | Polyneuropathy-predominant | Portugal, Japan, Sweden | 25–35 (early-onset) or 50–60+ (late-onset) |
| Val122Ile (V122I) | Cardiomyopathy-predominant | African Americans (3–4% carrier rate) | 60–70 |
| Thr60Ala (T60A) | Mixed cardiac/neuropathy | Ireland, Appalachian USA | 45–65 |
| Ser77Tyr (S77Y) | Cardiac-predominant | — | 50–70 |
| Ile84Ser (I84S) | Mixed phenotype | — | 40–60 |
| Leu111Met (L111M) | Cardiac-predominant | Denmark | 50–70 |
The Val30Met mutation accounts for approximately 70% of all hereditary ATTR cases worldwide. Three major endemic foci have been identified: northern Portugal (Póvoa de Varzim), northern Sweden (Skellefteå), and Japan (Nagano and Kumamoto prefectures) [5:1].
The Val122Ile variant is particularly significant from a public health perspective, as it is carried by 3–4% of African Americans (approximately 1.5 million individuals in the United States), making it one of the most common pathogenic mutations in any gene in the general population [6:1].
hATTR displays variable penetrance influenced by geographic origin, sex, and genetic modifiers. In Portuguese kindreds, penetrance approaches 80% by age 50, while in Swedish families, penetrance may be as low as 2% at age 30, increasing to 50% by age 60. [Male sex is associated with earlier onset and higher penetrance in most populations. Non-coding variants in the TTR gene and modifier genes affecting proteostasis pathways may influence disease expression] [7:1].
The neuropathic phenotype is the hallmark of hATTR, particularly with the Val30Met mutation:
Autonomic dysfunction is a prominent and often disabling feature:
Cardiac involvement is present in virtually all hATTR patients at some stage and is the primary determinant of prognosis:
Diagnosis requires a high index of suspicion, particularly in non-endemic areas. Red flags include:
The Coutinho staging system for polyneuropathy:
RNA interference (RNAi) and antisense oligonucleotide (ASO) therapies reduce hepatic TTR production by 80–90%:
Small molecules that bind to the thyroxine-binding sites on TTR, stabilizing the tetramer and preventing dissociation:
Orthotopic liver transplantation was the first disease-modifying treatment for hATTR, removing the primary source of mutant TTR. However, wild-type TTR produced by the donor liver can continue to deposit as amyloid, and the procedure carries significant morbidity and mortality. Liver transplantation has been largely supplanted by pharmacological therapies but remains an option in certain circumstances [8:1].
hATTR provides critical insights into broader neurodegenerative :
Without treatment, hATTR is invariably fatal, with median survival of 7–12 years from symptom onset for Val30Met neuropathy and 2–6 years for cardiac-predominant phenotypes. Disease-modifying therapies have dramatically altered the natural history: TTR gene silencers can stabilize or improve polyneuropathy, and TTR stabilizers reduce mortality in ATTR cardiomyopathy by approximately 30% over 30 months [9:1].
The study of Hereditary Transthyretin Amyloidosis (Hattr) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Recent advances in Hereditary Transthyretin Amyloidosis (hATTR) have focused on understanding disease , identifying , and developing novel therapeutic approaches. Key developments include:
Hawkins PN, Ando Y, Dispenzieri A, et al. Diagnosis and treatment of hereditary transthyretin amyloidosis (hATTR polyneuropathy). ↩︎
Adams D, Koike H, Slama M, Coelho T. Hereditary transthyretin amyloidosis: a model of medical progress for a fatal disease. Nat Rev Neurol. 2019. ↩︎ ↩︎
Ruberg FL, Berk JL. Transthyretin (TTR cardiac amyloidosis. Circulation. 2012. ↩︎ ↩︎
Pinto MV, Piras M, Shefner JM. Hereditary transthyretin amyloidosis: a comprehensive review with a focus on peripheral neuropathy). ↩︎
Planté-Bordeneuve V, Said G. Familial amyloid polyneuropathy. Lancet Neurol. 2011. ↩︎ ↩︎
Buxbaum JN, Ruberg FL. Transthyretin V122I (pV142I*—Not just a risk factor for cardiac amyloidosis. —Not just a risk factor for cardiac amyloidosis. 2017. ↩︎ ↩︎
Karam C, Dimitrova D, Engel WK, et al. Diagnosis and treatment of hereditary transthyretin amyloidosis with polyneuropathy in the United States). ↩︎ ↩︎
Garcia-Pavia P, Rapezzi C, Adler Y, et al. Transthyretin amyloid cardiomyopathy: from cause to novel treatments). ↩︎ ↩︎
Maurer MS, Kale P, Gundapaneni B, et al. Patisiran treatment in patients with transthyretin cardiac amyloidosis). ↩︎ ↩︎
Maurer MS, Schwartz JH, Gundapaneni B, et al. Tafamidis treatment for patients with transthyretin amyloid cardiomyopathy). ↩︎
Coelho T, Maurer MS, Suhr OB. Advances in the treatment of transthyretin amyloidosis). ↩︎
Fontana M, Martinez-Naharro A, Hawkins PN. Transthyretin amyloid cardiomyopathy: the plot thickens as novel therapies emerge). ↩︎