Mutant Transthyretin Research Articles

Liver Transplantation in Patients with Familial Amyloid Polyneuropathy: Comparison of Different Transthyretin Mutations

Introduction: Liver transplantation (LT) is the main option for patients with familial amyloid polyneuropathy (FAP). A wide variety of mutations are known in FAP. Depending on the underlying mutation the outcome of patients may differ considerably. Patients: Twenty-three patients with FAP (8 females, 15 males) underwent LT between 05/1998 and 07/2011. Transthyretin mutations included Val30Met (10 patients) and 10 other mutations. Symptoms: In almost all patients symptoms of polyneuropathy were present. Cardiac symptoms differed considerably. Arrhythmia was present in all but 4 patients with Val30Met mutation. 2 patients with Leu12Pro mutation suffered from severe seizures. 6/13 patients with non-Val30Met mutations presented cardiac symptoms. Treatment: In 6/10 patients with Val30Met mutation a cardiac pacemaker was implanted before LT. In 3 patients with non-Val30Met mutations combined heart-liver transplantation was deemed required (impaired systolic function, severe arrhythmia during attempted LT). In the first patient this approach was performed simultaneously, in the 3 following patients LT was performed several weeks after cardiac transplantation with a clinical course being less complicated. Outcome: 8 patients died after LT (5-year survival: 68 %). 2 patients with Val30Met mutation being older than 60 years of age died 1 month, the other 1 year after LT even they had no or mild impairment of cardiac function. 2 patients of the combined heart-liver transplanted group died: One because of cachexia 10 months after transplantation, the second after 115 months due to urosepsis. In the group of sole liver transplanted, two carriers of the Leu12Pro mutation died with complications of grandmal seizures, and both patients with Gly47Glu died of cardiac arrest even though respective symptoms were totally absent before LT. Conclusions: In younger patients with Val30Met mutation LT is the treatment of choice. It is consensus that LT should be performed as early as symptoms are recognised. The indication for implanting a pacemaker is questionable and obviously a defibrillator has to be preferred if required. In particular in patients with non-Val30Met mutations the indication of combined heart-liver transplantation depends on amyloid load of the heart and impaired systolic function. In general, indication for LT may be a problem in non-Val30Met.

Inability of Mutant Transthyretin V30M to Cross the Blood-Eye Barrier

Inability of Mutant Transthyretin V30M to Cross the Blood-Eye Barrier

Evaluation of tafamidis as first-line therapeutic agent for transthyretin familial amyloidotic polyneuropathy.

Almost 100 mutations in the human transthyretin (TTR) gene cause the autosomal dominant disorders of familial amyloidotic polyneuropathy (FAP) and familial amyloidotic cardiomyopathy. While these have been clinically classified as separate disorders, the peripheral and autonomic nervous systems and the heart are frequently involved in the same patient. Deposition of amyloid derived from a kinetically or thermodynamically unstable mutant TTR precursor produces an ascending sensorimotor polyneuropathy with marked autonomic involvement. Since 1990, treatment has been liver transplantation from a donor carrying two wild-type TTR genes, providing a crude form of gene therapy. Multiple studies have shown that small molecules fitting in the T4-binding pocket of TTR can stabilize the molecule, reducing its capacity to release the fibril precursor. Tafamidis is the first molecule to be tested in a placebo-controlled trial in patients with TTR-associated FAP. While the trial did not achieve its primary endpoints, it did stabilize TTR in vivo and had a favorable effect on some aspects of disease progression, particularly when administered early in the course. It may represent an alternative to liver transplantation, particularly in patients with early disease related to the V30M mutation. Longer-term studies are required to determine whether it represents a stabilizing or remittive form of treatment.

A case of familial amyloidotic polyneuropathy with a rare Phe33Leu mutation in the TTR gene

Department of Physiology, National Taiwan University College of Medicine, Taipei, TaiwanReceived 16 July 2012; accepted 23 July 2012Familial amyloidotic polyneuropathy (FAP) is a hereditarypolyneuropathy caused by transthyretin (TTR) mutation,and characterized by length-dependent sensorimotor pol-yneuropathy, autonomic dysfunction, and visceral organinvolvement.

Familial amyloidosis with polyneuropathy associated with TTR Ser50Arg mutation

Background: The phenotypic heterogeneity of transthyretin amyloidosis (ATTR) familial polyneuropathy may be linked to the type of mutation and to the environmental factors. A gender difference in relation to the severity of the disease has been suspected. More than 100 different pathogenic variants of hereditary transthyretin (TTR) mutations have been reported. Objective: To describe 32 patients with confirmed TTR Ser50Arg mutation from the same geographical origin. Methods: Seven families with up to four affected generations underwent genetic testing and prospective clinical and laboratory evaluations. Results: The mutation was confirmed in seven patients from different families with clinical symptoms compatible with ATTR amyloidosis, and in 25 (62%) of the 40 direct relatives tested. Of the 32 patients with positive test results, 18 (56%) were men. Only 5 (16%) subjects were disease-free at the time of the genetic test (mean age: 20, range: 18–30-year-old). The rest developed symptoms at a young age, between ages 36 and 41. Symptomatic, histologically positive patients were older than carriers and symptomatic patients without a confirmatory biopsy. The later generation displayed symptoms at a younger age. Initial manifestations in the 27 symptomatic patients were neuropathic in 19 (70%), gastrointestinal in 6 (22%) and autonomic in 1 (4%). Significant differences were demonstrated among genders, where men had a considerably worse outcome. Conclusion: ATTR Ser50Arg mutation was associated with an early onset, an unbalanced male to female ratio, a more aggressive course in males and possibly displayed anticipation.

Amyloidosis of the gastrointestinal tract: a 13-year, single-center, referral experience

Amyloidosis of the gastrointestinal tract, with biopsy-proven disease, is rare. We reviewed a series of patients who presented with biopsy-proven gastrointestinal amyloidosis and report their clinical characteristics, treatments, and survival. This is a retrospective review of data prospectively collected from January 1998 to December 2011 in a tertiary referral center; 2,334 patients with all types of amyloidosis were evaluated during this period. Seventy-six patients (3.2%) had biopsy-proven amyloid involvement of the gastrointestinal tract. Their median age was 61 years (range, 34-79). Systemic amyloidosis with dominant gastrointestinal involvement was present in 60 (79%) patients, whereas the other 16 (21%) patients had amyloidosis localized to the gastrointestinal tract without evidence of an associated plasma cell dyscrasia or other organ involvement. Of the 60 systemic cases, 50 (83%) had immunoglobulin light-chain, five (8%) had familial lysozyme, three (5%) had wild-type transthyretin, and two (3%) had mutant transthyretin amyloidosis. The most frequent symptoms for all patients were weight loss in 33 (45%) and gastrointestinal bleeding in 27 (36%). Incidental identification of amyloidosis on routine endoscopic surveillance played a role in the diagnosis of seven patients with systemic immunoglobulin light-chain, and four patients with immunoglobulin light-chain localized to the gastrointestinal tract. Amyloid protein subtyping was performed in 12 of the cases of localized disease, and all had lambda light chain disease. Of the 50 patients with systemic immunoglobulin light-chain amyloidosis, 45 were treated with anti-plasma cell therapy. The median survival has not been reached for this group. For the 16 patients with localized gastrointestinal amyloidosis, supportive care was the mainstay of treatment; none received anti-plasma cell therapy. All 16 are alive at a median follow-up of 36 months (range, 1-143). Patients with biopsy-proven gastrointestinal amyloidosis often present with weight loss and bleeding. In localized cases, all that underwent typing were due to lambda light chain amyloidosis and none progressed to systemic disease during the period of follow-up. Most patients with systemic disease had immunoglobulin light-chain, and their tolerance of therapy and median survival were excellent. Although a rare manifestation of amyloidosis, staining for amyloid should be considered in patients undergoing gastrointestinal biopsy who have unexplained chronic gastrointestinal symptoms.

Coagulation and fibrinolysis abnormalities in familial amyloid polyneuropathy

Objective: Familial amyloid polyneuropathy (FAP) is an autosomal dominant form of hereditary amyloidosis. Several studies reported coagulation factor X deficiency and excessive fibrinolysis in immunoglobulin light chain amyloidosis. However, few have investigated coagulation and fibrinolysis in FAP. The objective of this study was to determine abnormalities in plasma biomarkers of coagulation and fibrinolysis in FAP. Methods: We prospectively recruited eight FAP patients with transthyretin mutations and ten age-matched control patients with other neuropathies in our university. We examined plasma biomarkers of coagulation and fibrinolysis including prothrombin time, activated partial thromboplastin time, fibrinogen, fibrin/fibrinogen degradation products, D-dimer, α2-antiplasmin, antithrombin, plasminogen, thrombin-antithrombin complex, plasmin-α2-antiplasmin complex, prothrombin fragment 1+2, and coagulation factor X. The Mann–Whitney U test was performed for statistical comparisons between FAP and control groups. Results: FAP patients exhibited significantly decreased levels of coagulation factor X, plasminogen and α2-antiplasmin, and significantly increased levels of prothrombin fragment 1+2 compared to control patients. Conclusion: Our results indicate abnormalities of coagulation and fibrinolysis in FAP patients.

Transthyretin Amyloidosis and the Kidney

The amyloidoses are protein-misfolding disorders associated with progressive organ dysfunction. Immunoglobulin light chain is the most common, amyloid A the longest recognized, and transthyretin-associated amyloidosis (ATTR) the most frequent inherited systemic form. Although ATTR, an autosomal-dominant disease, is associated with at least 100 different transthyretin (TTR) mutations, the single amino-acid substitution of methionine for valine at position 30 is the most common mutation. Each variant has a different organ involvement, although clinical differences attributed to environmental and genetic factors exist within the same mutation. Peripheral neuropathy and cardiomyopathy are broadly described, and insights into disease reveal that kidney impairment and proteinuria are also clinical features. This review combines clinical and laboratory findings of renal involvement from the main geographic regions of disease occurrence and for different mutations of TTR. Fifteen nephropathic variants have been described, but the TTR V30M mutation is the best documented. Nephropathy affects patients with late-onset neuropathy, low penetrance in the family, and cardiac dysrhythmias. Microalbuminuria can be the disorder's first presentation, even before the onset of neuropathy. Amyloid renal deposits commonly occur, even in the absence of urinary abnormalities. The experience with renal replacement therapy is based on hemodialysis, which is associated with poor survival. Because TTR is synthesized mainly in the liver, liver transplantation has been considered an acceptable treatment; simultaneous liver-kidney transplantation is recommended to avoid recurrence of nephropathy. In addition, the kidney-safety profile of new drugs in development may soon be available.

Cardiac involvement in hereditary-transthyretin related amyloidosis

Hereditary transthyretin-related amyloidosis remains a widely underdiagnosed condition, owing to its extreme phenotypic variability: the clinical spectrum of the disease ranges from an almost exclusive neurologic involvement to strictly cardiac manifestations. This heterogeneity is linked to several factors including specific transthyretin mutations, geographic distribution and endemic vs. non-endemic aggregation type. The existence of exclusively or predominantly cardiac phenotypes makes the recognition of the disease very challenging since it can mimic other more common causes of left ventricular “hypertrophy”. Assessment of such patients should include an active search for possible red flags that can indicate the correct final diagnosis.

Cardiac Amyloidosis Mimicking Hypertrophic Cardiomyopathy With Obstruction: Treatment With Disopyramide

A 71-year old-man presented with 4 posturally related syncopal episodes. He carried a diagnosis of asymptomatic hypertrophic cardiomyopathy (HCM) without obstruction based on an echocardiogram 7 years earlier. Echocardiography at the time of syncope evaluation demonstrated a hyperdynamic left ventricle with a septal thickness of ≈20 mm (an increase of 4 mm from an earlier echocardiogram), newly present systolic anterior motion of the mitral valve, and a peak left ventricular (LV) outflow tract gradient of 42 mm Hg at rest and 120 mm Hg with Valsalva maneuver (Figure 1). He was referred for septal myectomy, and cardiac catheterization demonstrated nonobstructive coronary artery disease. An ECG showed low-voltage limb leads, unusual in HCM (Figure 2), and cardiac magnetic resonance imaging (MRI) revealed delayed gadolinium enhancement in the papillary muscles, transmural enhancement involving the basal lateral walls, and subendocardial enhancement of the basal, mid, and distal anterior walls. There was also extensive gadolinium uptake in the atrial walls (Figure 3). Because the cardiac MRI suggested an infiltrative process, a cardiac biopsy was performed. This demonstrated extensive amyloid infiltration (Figure 4). Immunohistochemistry was positive for transthyretin, but negative for amyloid A and κ/λ light chains. Genetic testing for common mutations associated with HCM was negative, and no transthyretin mutations were detected. A diagnosis …

Why are some amyloidoses systemic? Does hepatic “chaperoning at a distance” prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

In the human systemic amyloidoses caused by mutant or wild-type transthyretin (TTR), deposition occurs at a distance from the site of synthesis. The TTR synthesized and secreted by the hepatocyte circulates in plasma, then deposits in target tissues far from the producing cell, a pattern reproduced in mice transgenic for multiple copies of the human wild-type TTR gene. By 2 yr of age, half of the transgenic males show cardiac deposition resembling human senile systemic amyloidosis. However, as early as 3 mo of age, when there are no deposits, cardiac gene transcription differs from that of nontransgenic littermates, primarily in the expression of a large number of genes associated with inflammation and the immune response. At 24 mo, the hearts with histologically proven TTR deposits show expression of stress response genes, exuberant mitochondrial gene transcription, and increased expression of genes associated with apoptosis, relative to the hearts without TTR deposition. These 24-mo-old hearts with TTR deposits also show a decrease in transcription of inflammatory genes relative to that in the younger transgenic mice. After 2 yr of expressing large amounts of human TTR, the livers of the transgenic mice without cardiac deposition display chaperone gene expression and evidence of an activated unfolded protein response, while the livers of animals with cardiac TTR deposition display neither, showing increased transcription of interferon-responsive inflammatory genes and those encoding an antioxidant response. With time, in animals with cardiac deposition, it appears that hepatic proteostatic capacity is diminished, exposing the heart to a greater load of misfolded TTR with subsequent extracellular deposition. Hence systemic (cardiac) TTR deposition may be the direct result of the diminution in the distant chaperoning capacity of the liver related to age or long-standing exposure to misfolded TTR, or both.

Epigallocatechin-3-Gallate as a Potential Therapeutic Drug for TTR-Related Amyloidosis: “In Vivo” Evidence from FAP Mice Models

BackgroundFamilial amyloidotic polyneuropathy (FAP) is a neurodegenerative disease caused by the extracellular deposition of mutant transthyretin (TTR), with special involvement of the peripheral nervous system (PNS). Currently, hepatic transplantation is considered the most efficient therapy to halt the progression of clinical symptoms in FAP since more than 95% of TTR is produced by the liver. However, less invasive and more reliable therapeutic approaches have been proposed for FAP therapy, namely based on drugs acting as inhibitors of amyloid formation or as amyloid disruptors. We have recently reported that epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, is able to inhibit TTR aggregation and fibril formation, “in vitro” and in a cellular system, and is also able to disrupt pre-formed amyloid fibrils “in vitro”.Methodology and Principal FindingsIn the present study, we assessed the effect of EGCG subchronic administration on TTR amyloidogenesis “in vivo”, using well characterized animal models for FAP. Semiquantitative immunohistochemistry (SQ-IHC) and Western blot analysis of mice tissues after treatment demonstrated that EGCG inhibits TTR toxic aggregates deposition in about 50% along the gastrointestinal tract (GI) and peripheral nervous system (PNS). Moreover EGCG treatment considerably lowered levels of several biomarkers associated with non-fibrillar TTR deposition, namely endoplasmic reticulum (ER)-stress, protein oxidation and apoptosis markers. Treatment of old FAP mice with EGCG resulted not only in the decrease of non-fibrillar TTR deposition but also in disaggregation of amyloid deposits. Consistently, matrix metalloproteinase (MMP)-9 and serum amyloid P component (SAP), both markers of amyloid deposition, were also found reduced in treated old FAP mice.Conclusions and SignificanceThe dual effect of EGCG both as TTR aggregation inhibitor and amyloid fibril disruptor together with the high tolerability and low toxicity of EGCG in humans, point towards the potential use of this compound, or optimized derivatives, in the treatment of TTR-related amyloidoses.

Clusterin Overexpression and Its Possible Protective Role in Transthyretin Deposition in Familial Amyloidotic Polyneuropathy

Extracellular chaperones such as clusterin may contribute to extracellular protein homeostasis in neurodegenerative disorders. It has been implicated in fibrillogenesis and extracellular misfolded protein clearance in Alzheimer disease. We investigated the localization and potential functions of clusterin in familial amyloidotic polyneuropathy (FAP), a neurodegenerative disorder characterized by extracellular deposition of mutant transthyretin (TTR) in the peripheral nervous system. We observed increased clusterin expression in human FAP nerves, in the dorsal root ganglia of mutant TTR transgenic mice with TTR deposition, and in human neuroblastoma cells incubated with oligomeric TTR. Clusterin colocalized with extracellular TTR aggregates in human FAP nerves and was detected in aggregates extracted from FAP tissues. Abolition of clusterin expression using small interfering RNA in a HEK293 cell line that secretes wild-type TTR resulted in increased TTR aggregation in the medium, thus suggesting a protective role for clusterin in inhibition of TTR aggregation. However, under the conditions examined, toxicity of oligomeric TTR in neuroblastoma cells was unaltered by clusterin gene silencing. These data suggest that clusterin can influence TTR aggregation but may not modulate TTR aggregate toxicity or play a role in TTR clearance in FAP. Further studies will elucidate neuroprotective mechanisms conferred by clusterin in FAP and other neurodegenerative diseases.

Cardiac phenotype and clinical outcome of familial amyloid polyneuropathy associated with transthyretin alanine 60 variant

Familial amyloid polyneuropathy (FAP) is a dominantly inherited multi-system disease associated with transthyretin (TTR) mutations. Previous series have predominantly described patients with the TTR variant Val30Met (V30M), which is the most prevalent cause of FAP worldwide. Here, we report the dominant cardiac phenotype and outcome of FAP associated with TTR Thr60Ala (T60A), the most common UK variant. Sixty consecutive patients with FAP associated with TTR T60A (FAP T60A) were prospectively evaluated in two centres between 1992 and 2009. Median (range) age of symptom development was 63 (45-78) years. A family history of amyloidosis was present in only 37%. Autonomic and peripheral neuropathy were present in 44 and 32 patients, respectively, at diagnosis. Cardiac involvement was evident on echocardiography at diagnosis in 56 patients, but was associated with reduced QRS voltages on electrocardiography in only 16% evaluable cases. Seventeen patients received implantable anti-arrhythmic devices. Median survival was 6.6 years following onset of symptoms and 3.4 years from diagnosis, and correlated with serum N-terminal prohormone brain natriuretic peptide (NT-proBNP) concentration and certain echocardiographic parameters at the latter. Orthotopic liver transplantation (OLT), performed to eliminate the predominant hepatic source of variant TTR T60A protein, was performed in eight patients including one who received a concomitant cardiac transplant. Cardiac amyloidosis progressed in all lone OLT recipients, of whom four died within 5 years. Cardiac amyloidosis is almost always present at diagnosis in FAP T60A, and is a major determinant of its poor prognosis. Outcome of liver transplantation in FAP T60A has been discouraging.

P72 Liver transplantation for familial amyloidosis; long-term data from the Familial Amyloid Polyneuropathy World Transplant Registry (FAPWTR)

IntroductionLiver transplantation (LT) is the only available treatment for familial amyloid polyneuropathy (FAP). The Familial Amyloid Polyneuropathy World Transplant Registry (FAPWTR), established shortly after LT was introduced as potential treatment...

Role of 99mTc-DPD Scintigraphy in Diagnosis and Prognosis of Hereditary Transthyretin-Related Cardiac Amyloidosis

In a cohort of patients with hereditary transthyretin-related amyloidosis (ATTR), we aimed to assess the role of (99m)Tc-3,3-diphosphono-1,2-propanodicarboxylic acid ((99m)Tc-DPD) in detecting myocardial amyloid infiltration across a wide spectrum of cardiac involvement and in predicting major adverse cardiac events (MACE). Hereditary transthyretin-related amyloidosis is a challenging and underdiagnosed condition where both early diagnosis and prognosis remain problematic. We evaluated 63 patients with ATTR: 40 with and 23 without echocardiographically diagnosed amyloidotic cardiomyopathy (AC). Myocardial uptake of (99m)Tc-DPD scintigraphy was semiquantitatively and visually assessed at 5 min and 3 h. All patients with AC showed moderate-to-severe myocardial tracer uptake (i.e., visual score ≥2). Within the subgroup without AC, only 4 patients (with Ala36Pro, Gly47Ala, Thr49Ala, and Glu89Gln transthyretin mutations) showed myocardial tracer uptake and abnormal heart/whole body retention (H/WB) values: in all these cases endomyocardial biopsies showed amyloidotic infiltration. The H/WB was positively correlated with left ventricular (LV) mean wall thickness (Pearson's r=0.695, p<0.001) and negatively with LV ejection fraction (r=-0.368, p=0.004). The H/WB was an unfavorable predictor of MACE-free survival at Cox univariate analysis and contributed to the multivariate model. Notably, LV wall thickness >12 mm in combination with H/WB >7.5 was associated with the highest event rate. In ATTR, (99m)Tc-DPD scintigraphy can identify myocardial infiltration across a wide spectrum of morphologic/functional cardiac involvement, allowing an early diagnosis of the disease (even before the appearance of echocardiographic abnormalities). The (99m)Tc-DPD myocardial uptake is a prognostic determinant of "cardiac" outcome in ATTR, either alone or in combination with LV wall thickness.

Transthyretin gene V30M, H90N, and (del9) mutations in cardiomyopathy patients from St. Petersburg

A search of transthyretin (TTP) gene mutations was conducted in patients with cardiomyopathies from St. Petersburg. Mutations H90N, V30M, G47A, and deletion (del9) of nucleotides GACTTCTCC in position 6776 from the start codon of the TTP gene (in position 98782 according to reference sequence AC079096 (NCBI) was found. The H90N mutation in the third exon of TTP gene was detected in a son of a cardiomyopathy patient and in his mother, which lacked any clinical manifestations. Mutations V30M and G47A in exon 2 of TTP gene were found in heterozygous and homozygous state, respectively, in one of the probands. Deletion (del9) was revealed in a patient with cardiomyopathy and in his two daughters from different marriages, who had no clinical manifestations of the disease. All the mutations revealed in this study were previously identified in other populations.

Coincidental Gammopathies In Patients with Systemic Amyloidosis and Transthyretin Gene Mutations

AbstractAbstract 2948Systemic AL amyloidosis is a proteotoxic clonal plasma cell disorder in which amyloid-forming immunoglobulin light chains produced by the clonal plasma cells cause cellular toxicity and deposit as fibrils, leading to organ dysfunction and death, usually of a cardiac cause. Distinguishing AL from other types of amyloidosis such as senile systemic due to wildtype (ATTRwt), or hereditary due to mutant transthyretin (ATTRm), can be challenging and has significant clinical ramifications. The incidence of monoclonal gammopathies (MG) is increased in African-Americans and in older patients; patients in those categories who have ATTRwt or ATTRm are more likely to have MG and are therefore at increased risk of being misdiagnosed with AL and receiving cytotoxic chemotherapy inappropriately.Over a 6 year period at Memorial Sloan-Kettering Cancer Center, 369 consecutive patients with systemic amyloidosis were evaluated for clonal plasma cell disease and 30% of them were screened for hereditary ATTRm based on African-American race, dominant peripheral neuropathy or having been referred with a tissue diagnosis of amyloidosis without apparent MG. A mutant transthyretin was identified in 5.4% (20/369; 7 Ala60Thr, 4 Ile122Val (one homozygote), 4 Phe64Leu, 4 Val30Met and 1 Glu89Gln). In addition, ATTRwt was diagnosed in 4% (15/369). Of the 20 consecutive patients with mutant TTR, 10 had an associated gammopathy, 6 monoclonal and 4 polyclonal. Those with MG had 2 potential sources of amyloidogenic proteins - the light chains associated with the MG and the mutant TTR. We used several available approaches to establish a conclusive diagnosis, including immunohistochemistry (IHC) and more definitive typing via mass spectrometry (MS) and immunogold electron microscopy (IEM). Ultimately, 4 of the 6 with MG and mutant TTR were diagnosed with ATTRm, while the other 2 had AL amyloidosis and were treated with chemotherapy. Of note, one patient was initially thought to have ATTRm based on IHC, but then shown to have AL based on MS. Interestingly, none of the 15 consecutive patients with SSA had a gammopathy despite being an older cohort (med age 76.5 vs 64). This lends credence to the hypothesis that patients with TTR mutations may be at increased risk of developing gammopathies (50% in this series). The significance of this rate of coincidence is two-fold. First, the mutant TTR protein may be immunogenic, as has been suggested.1 Second, this heightens the need for diagnostic vigilance and willingness to perform direct tissue typing. Kindreds with hereditary disease may be at greater risk of being misdiagnosed and treated for AL then would be expected based on population wide incidence. Clinical diligence and use of the newest techniques for pathologic typing are essential.2O'Nuallain B, Hrncic R, Wall JS, Weiss DT, Solomon A. Diagnostic and therapeutic potential of amyloid-reactive IgG antibodies contained in human sera. J Immunol. 2006 Jun 1;176(11):7071-8.Vrana J, Gamez J, Madden B, Theis J, Bergen H, Dogan A. Classification of amyloidosis by laser microdissection and mass spectrometry based proteomic analysis in clinical biopsy specimens. Blood. 2009. Dec 3; 114(24):4957-9. Disclosures:Comenzo:Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Elan Pharmaceuticals: Consultancy; Genzyme: Research Funding; Celgene: Research Funding; Ortho: Research Funding.

A possible role for miRNA silencing in disease phenotype variation in Swedish transthyretin V30M carriers

BackgroundFamilial amyloidosis with polyneuropathy (FAP) is an autosomal dominant disease caused by transthyretin (TTR) mutations, of which V30M (TTR c.148G > A, p.Val50Met, "Val30Met") is the most common. Swedish V30M carriers display later age at onset and lower penetrance compared to other populations.MethodsIn the study, 130 Swedish V30M carriers (32 early, 30 late onset and 68 asymptomatic carriers) and 50 controls, 23 French symptomatic V30M carriers and 29 controls and 18 Japanese symptomatic V30M carriers and 29 controls were included. We aimed to identify additional genetic factors in the TTR gene and its surrounding region that could have an impact on phenotype.ResultsWe identified three SNPs (rs71383038, rs3794885 and rs62093482) with a significant difference in allele frequency between Swedish V30M carriers and controls. The two Swedish V30M homozygous patients present in the study also displayed homozygosity for the CA10 (rs71383038), A (rs3794885) and T (rs62093482) alleles in these SNPs. Hence, these alleles are present on the Swedish V30M haplotype. Of these, rs62093482 is located in the 3'UTR of TTR gene and thus more interesting since SNPs in the 3'UTR can affect gene expression levels by modifying microRNA (miRNA) targeting activity. miRNA target predictions revealed four potential miRNAs with predicted targets unique for the polymorphic allele.ConclusionsOur results are the first to show the presence of a 3'UTR polymorphism on the V30M haplotype in Swedish carriers, which can serve as a miRNA binding site potentially leading to down-regulated expression from the mutated TTR allele. This finding may be related to the low penetrance and high age at onset of the disease observed in the Swedish patient population.

Pathology and functional diagnosis of small-fiber painful neuropathy.

Small-fiber sensory neuropathy with neuropathic pain had been a diagnostic challenge for neurologists. We and several groups have developed skin biopsy with quantitation of intraepidermal nerve fiber (IENF) density as a diagnostic approach. In the skin with small-fiber sensory neuropathy, there are pathological hallmarks: reduced IENF density with degeneration of subepidermal nerve plexuses and dermal nerves. Skin denervation is a major presentation of diabetic neuropathy and inflammatory neuropathies including Guillain-Barr syndrome and chronic inflammatory demyelinating polyneuropathy. The skin biopsy approach also provides an opportunity to examine dermal vasculature and inflammatory vasculopathy is demonstrated in vasculitic neuropathy, systemic lupus erythematosus, and eosinophilia-associated neuropathy. In addition to neuropahtologic evidence, the functional consequences of cutaneous nerve degeneration can be assessed with quantitative sensory testing (QST), contact heat evoked potential (CHEP), and functional magnetic resonance imaging (fMRI). One major etiology of small-fiber sensory neuropathy is familial amyloid polyneuropathy caused by mutations of transthyretin (TTR). We recently conducted studies on a large cohort of unique TTR mutation on Ala97Ser in Taiwan. These patients had significant skin denervation in addition to motor and autonomic neuropathy. Taken together, the skin biopsy with quantitation of IENF density provides diagnostic utility for small-fiber sensory neuropathy and the combination of psychophysical, physiological, and neuroimaging examinations offer comprehensive assessments for patients with neuropathic pain due o cutaneous nerve degeneration.