Disease risk estimates in V30M variant transthyretin amyloidosis (A-ATTRv) from Mallorca.

BACKGROUND: Variant transthyretin amyloidosis (A-ATTRv) is an autosomal dominant disease caused by a range of TTR gene variants which entail great phenotypical heterogeneity and penetrance. In Majorca, the A-ATTRv caused by the V30M gene variant (A-ATTRV30M) is the most common. Since asymptomatic carriers are at risk of developing the disease, estimating age of onset is vital for proper management and follow-up. Thus, the aim of this study was to estimate age-related penetrance in ATTRV30M variant carriers from Majorca. METHODS: The disease risk among carriers from ATTRV30M families from Majorca was estimated by Non-parametric survival estimation. Factors potentially involved in the disease expression, namely gender and parent of origin were also analysed. RESULTS: A total of 48 heterozygous ATTRV30M families (147 affected patients and 123 were asymptomatic carriers) were included in the analysis. Penetrance progressively increased from 6% at 30 years to 75% at 90 years of age. In contrast to other European populations, we observe a similar risk for both males and females, and no difference of risk according to the parent of origin. CONCLUSIONS: In this first study assessing the age-related penetrance of ATTRV30M variant in Majorcan families, no effect of gender or parent of origin was observed. These findings will be helpful for improving management and follow-up of TTR variant carrier individuals.

Early data on long-term efficacy and safety of inotersen in patients with hereditary transthyretin amyloidosis: a 2-year update from the open-label extension of the NEURO-TTR trial.

BACKGROUND AND PURPOSE: Hereditary transthyretin (hATTR) amyloidosis causes progressive polyneuropathy resulting from transthyretin (TTR) amyloid deposition throughout the body, including the peripheral nerves. The efficacy and safety of inotersen, an antisense oligonucleotide inhibitor of TTR protein production, were demonstrated in the pivotal NEURO-TTR study in patients with hATTR polyneuropathy. Here, the long-term efficacy and safety of inotersen are assessed in an ongoing open-label extension (OLE) study. METHODS: Patients who completed NEURO-TTR were eligible to enroll in the OLE (NCT02175004). Efficacy assessments included the modified Neuropathy Impairment Score plus seven neurophysiological tests composite score (mNIS + 7), the Norfolk Quality of Life - Diabetic Neuropathy (Norfolk QOL-DN) questionnaire total score and the Short-Form 36 Health Survey (SF-36) Physical Component Summary (PCS) score. Safety and tolerability were also assessed. RESULTS: Overall, 97% (135/139) of patients who completed NEURO-TTR enrolled in the OLE. Patients who received inotersen for 39 cumulative months in NEURO-TTR and the OLE continued to show benefit; patients who switched from placebo to inotersen in the OLE demonstrated improvement or stabilization of neurological disease progression by mNIS + 7, Norfolk QOL-DN and SF-36 PCS. No new safety concerns were identified. There was no evidence of increased risk for grade 4 thrombocytopenia or severe renal events with increased duration of inotersen exposure. CONCLUSION: Inotersen slowed disease progression and reduced deterioration of quality of life in patients with hATTR polyneuropathy. Early treatment with inotersen resulted in greater long-term disease stabilization than delayed initiation. Routine platelet and renal safety monitoring were effective; no new safety signals were observed.

Usefulness of T2 ratio in the diagnosis and prognosis of cardiac amyloidosis using cardiac MR imaging.

PURPOSE: To detect if a difference of T2 ratio, defined as the signal intensity (SI) of the myocardium divided by the SI of the skeletal muscle on T2-weigthed cardiac magnetic resonance (CMR) imaging, exists between patients with systemic amyloidosis, by comparison to control subjects. To determine if a relationship exists between T2 ratio and the overall mortality. MATERIALS AND METHODS: CMR imaging examinations of 73 consecutive patients (48 men, 25 women; mean age, 63 years±15[SD]) with amyloidosis and suspicion of CA and 27 control subjects were retrospectively analyzed after institutional review board approval. Final diagnosis of CA was retained in case of histological confirmation of CA, typical pattern of CA on imaging and/or positivity of 99Technetium-hydroxymethylene diphosphonate scintigraphy. Patients were divided in 2 groups according to the presence or the absence of CA. T2 ratios were calculated in patients with and those without CA and in control subjects with using analysis of variance. Prognostic value of T2 ratio was studied with a Kaplan-Meier curve. RESULTS: Thirty-five patients (51%) had CA and 33 (49%) were free from CA. T2 ratio was lower in patients with CA (1.18±0.29) than in patients without cardiac involvement (1.37±0.35) (P=0.03) and control subjects (1.45±0.24) (P=0.004). A T2 ratio of 1.36 was the best threshold value for predicting CA with a sensitivity of 63% and a specificity of 73%. Kaplan-Meier analysis showed a significant relationship between a shortened overall survival and a T2 ratio<1.36. CONCLUSION: Patients with CA exhibit lower T2 ratio on CMR imaging by comparison with patients free of CA and control subjects.

Diagnosis of small fiber neuropathy: A comparative study of five neurophysiological tests.

The diagnosis of small fiber neuropathy (SFN) is a challenge for clinical neurophysiology. Conventional nerve conduction studies are inappropriate for this purpose and therefore various neurophysiological tests have been proposed. In this study, we compared the diagnostic value of five of these tests in 87 patients with clinically definite (n=33) or possible (n=54) SFN related to amyloid neuropathy secondary to transthyretin gene mutation or monoclonal gammopathy (n=30), primary Sjögren's syndrome (n=20), Fabry's disease (n=2), or unknown cause (n=35). Neurophysiological tests included quantitative sensory testing with determination of warm and cold detection thresholds (WDT, CDT), recording of laser-evoked potentials (LEP) and sympathetic skin responses (SSRs), and measurement of electrochemical skin conductance (ESC) using Sudoscan(®) device. All tests were performed at the four extremities (hands and feet). All patients with clinically definite SFN and 70% of the patients with possible SFN had at least one abnormal test. The LEP was the most sensitive test (altered in 79% of the patients with at least one abnormal test), followed by ESC (61%), WDT (55%), SSR (41%), and CDT (32%). The combination of LEP, assessing A-delta sensory fibers, WDT, assessing sensory C fibers, and ESC, assessing autonomic C fibers, appears a relevant approach for the diagnosis of SFN. Compared to SSR and CDT, these three tests, LEP, WDT, and ESC, had a significantly better diagnostic sensitivity and their combination further improved diagnostic accuracy.

Transthyretin familial amyloid polyneuropathy.

TTR FAP is characterized by phenotypic and genotypic heterogeneity. The severity of polyneuropathy along with autonomic dysfunction and heart involvement makes it a life-threatening disease. This protein is mainly produced by the liver. Molecular genetic testing is essential in the diagnostic strategy. TTR-Val30Met is the most frequent substitution, resulting in a guanine to cytosine mutation in exon 2 of the gene. It is virtually the only variant detected in Portugal, Brazil, and Sweden. By contrast, as many as 30 different TTR variants are reported in Japan and in other European countries. A less severe phenotype with late onset has been reported. Diagnosis should be performed as early as possible since upcoming pharmacological therapeutic approaches are now available, in addition to liver transplantation.

Penetrance estimation of TTR familial amyloid polyneuropathy (type I) in Brazilian families.

BACKGROUND AND PURPOSE: Familial amyloid polyneuropathy (FAP) type I is a severe autosomal dominant inherited neuropathy associated with mutations in the transthyretin (TTR) gene. Significant phenotypic variability is seen amongst families with distinct geographic origin, especially regarding penetrance and age of onset. The aim of this study was to estimate the penetrance of FAP in Brazilian families. METHODS: Twenty-two distinct families were ascertained through genetically confirmed index cases and included in this study. Genealogical and clinical data were obtained from a total of 623 individuals, including 126 affected by FAP. In 15 families, TTR genotyping was performed in all available relatives (n = 86), after informed written consent. Seven families did not consent for genetic testing, but agreed to provide clinical and genealogical data. Penetrance was estimated using a previously described method based on survival analysis and corrected for ascertainment bias. RESULTS: Mean age of onset in our sample was 34.5 years, with a significant earlier onset in males (31.1 vs. 35.9, P < 0.0001). The penetrance of FAP in our sample was estimated as 83% (95% CI: 66-99) after 60 years. CONCLUSION: Our results provide new information on FAP in Brazilian patients and may be helpful in the genetic counseling of this population.

Discordant expression of familial amyloid polyneuropathy in monozygotic Brazilian twins.

Discordant expression of Familial Amyloid Neuropathy (FAP) in monozygotic twins is a rare event. Only five such cases have been described in the literature so far. We report the clinical, neurophysiologic and autonomic findings of Brazilian monozygotic twins discordant for the expression of FAP type I. Twin I first presented symptoms at the age of 21, when his brother was completely asymptomatic. Twin 2 only presented symptoms at the age of 25, almost four years after his brother. Both brothers eventually developed the complete phenotype of FAP type I. The occurrence of monozygotic twins discordant for the expression of FAP type I suggests that other factors beside TTR gene mutations should play an important role in the pathogenesis of this condition. Environmental factors, as well as modifier genetic loci are likely to modulate the expression of FAP type I and the study of cases such as the one presented here may help to identify some of these factors.

PEL: an unbiased method for estimating age-dependent genetic disease risk from pedigree data unselected for family history.

Providing valid risk estimates of a genetic disease with variable age of onset is a major challenge for prevention strategies. When data are obtained from pedigrees ascertained through affected individuals, an adjustment for ascertainment bias is necessary. This article focuses on ascertainment through at least one affected and presents an estimation method based on maximum likelihood, called the Proband's phenotype exclusion likelihood or PEL for estimating age-dependent penetrance using disease status and genotypic information of family members in pedigrees unselected for family history. We studied the properties of the PEL and compared with another method, the prospective likelihood, in terms of bias and efficiency in risk estimate. For that purpose, family samples were simulated under various disease risk models and under various ascertainment patterns. We showed that, whatever the genetic model and the ascertainment scheme, the PEL provided unbiased estimates, whereas the prospective likelihood exhibited some bias in a number of situations. As an illustration, we estimated the disease risk for transthyretin amyloid neuropathy from a French sample and a Portuguese sample and for BRCA1/2 associated breast cancer from a sample ascertained on early-onset breast cancer cases.

Mitochondrial haplogroup is associated with the phenotype of familial amyloidosis with polyneuropathy in Swedish and French patients.

Familial amyloidotic polyneuropathy (FAP) is a monogenic disease caused by mutations in the transthyretin (TTR) gene. The phenotype of the most common TTR mutation, V30M, varies within and between populations. Oxidative stress and protein misfolding are cellular processes involved in the development of FAP. Because the mitochondria are important for both these processes, we investigated if mitochondrial haplogroups are related to age at onset of the disease in Swedish and French FAP patients. Mitochondrial haplogroup analysis was performed on 25 early-onset (below 40 years) and 29 late-onset (above 51 years) Swedish FAP patients. DNA from 249 Swedish individuals served as controls. In addition, 6 early-onset and 17 late-onset French FAP patients were examined with 25 French controls. The haplogroup distribution among late-onset Swedish and French cases was similar to that found in the general populations, whereas among early-onset cases a different haplogroup distribution was seen. The relatively rare haplogroup K was significantly more common among early-onset cases. Our findings substantiate the suggestion that a genetic component, still to be found, affecting mitochondrial function has an impact on the amyloid generating process in transthyretin amyloidosis.

On the origin of the transthyretin Val30Met familial amyloid polyneuropathy.

Transthyretin (TTR) familial amyloid polyneuropathy is a severe autosomal dominant neuropathy of adulthood, frequently linked to the pathogenic Val30Met variant of the TTR gene. The condition was initially described in northern Portugal, which is the first focus of the disease. Other important clusters of families are found in Sweden, Japan and South America. The origin of the Val30Met mutation and its distribution through the populations remains unclear. In the present work, we aimed at refining the history of the Val30Met mutation in patients affected with TTR amyloid neuropathy from Portugal, Sweden and Brazil. The decay of haplotype sharing was studied in 60 patients to estimate the age of the Most Recent Common Ancestor (MRCA) of mutation carriers in these populations. Our results showed a common haplotype in Portuguese and Brazilian patients and an age estimate of the MRCA of 750 and 650 years, respectively. In contrast, a different haplotype was found in the Swedish Val30Met patients with a corresponding age estimate for the MRCA, of 375 years. This work strengthens the hypothesis of different founders in Portuguese and Swedish Val30Met carriers and suggested a Portuguese origin of the Brazilian mutation. The age estimates of the MRCA are in line with the current historical knowledge of these populations.

A brief compound test for assessment of autonomic and sensory-motor dysfunction in familial amyloid polyneuropathy.

BACKGROUND: Familial amyloid polyneuropathies (FAP) patients manifest progressive sensory-motor length dependent polyneuropathy and severe autonomic dysfunction. In this setting the autonomic manifestations include mainly postural hypotension, nausea and vomiting, diarrhea and constipation, sphincter distur- bances and erectile dysfunction. Reproducible quantitative evaluation of signs and symptoms are necessary for the assessment of treatment efficacy. OBJECTIVE: To determine the reliability of a new compound test cumulating evaluation of autonomic and sensorymotor dysfunction in FAP. METHODS: Compound Autonomic Dysfunction Test (CADT) is a new questionnaire to evaluate the main symptoms of autonomic dysfunction observed in FAP. A separate functional questionnaire assesses the disability due to the sensorymotor deficit (Modified Norris Test; MNT). The compound test takes approximately 10 minutes to perform. In this prospective study, we enrolled consecutively 60 FAP patients to test interexaminer reliability, i.e., both questionnaires rated independently by 2 examiners. We also evaluate the reliability of testing patients face to face and by phone call, by the same examiner. RESULTS: Interexaminer reliabilities tested were high (ICC=0.92 for the CADT, p < 0.001; and ICC = 0.99 for the MNT, p < 0.001). In addition, testing by phone as compared to testing during the initial medical visit by the same investigator gave similar results (ICC = 0.91 for the CADT, p < 0.001; and ICC = 0.98 for the MNT, p < 0.001). CONCLUSION: In FAP, the CADT and the MNT have good reliability inter-investigators as well as between face to face and by phone call, by the same examiner. This newly designed compound test is a simple and reproducible scale which is adapted to evaluate the main neuropathic manifestations and will be useful for assessment of future treatments in this condition.

Diagnostic pitfalls in sporadic transthyretin familial amyloid polyneuropathy (TTR-FAP).

Transthyretin familial amyloid polyneuropathies (TTR-FAPs) are autosomal dominant neuropathies of fatal outcome within 10 years after inaugural symptoms. Late diagnosis in patients who present as nonfamilial cases delays adequate management and genetic counseling. Clinical data of the 90 patients who presented as nonfamilial cases of the 300 patients of our cohort of patients with TTR-FAP were reviewed. They were 21 women and 69 men with a mean age at onset of 61 (extremes: 38 to 78 years) and 17 different mutations of the TTR gene including Val30Met (38 cases), Ser77Tyr (16 cases), Ile107Val (15 cases), and Ser77Phe (5 cases). Initial manifestations included mainly limb paresthesias (49 patients) or pain (17 patients). Walking difficulty and weakness (five patients) and cardiac or gastrointestinal manifestations (five patients), were less common at onset. Mean interval to diagnosis was 4 years (range 1 to 10 years); 18 cases were mistaken for chronic inflammatory demyelinating polyneuropathy, which was the most common diagnostic error. At referral a length-dependent sensory loss affected the lower limbs in 2, all four limbs in 20, and four limbs and anterior trunk in 77 patients. All sensations were affected in 60 patients (67%), while small fiber dysfunction predominated in the others. Severe dysautonomia affected 80 patients (90%), with postural hypotension in 52, gastrointestinal dysfunction in 50, impotence in 58 of 69 men, and sphincter disturbance in 31. Twelve patients required a cardiac pacemaker. Nerve biopsy was diagnostic in 54 of 65 patients and salivary gland biopsy in 20 of 30. Decreased nerve conduction velocity, increased CSF protein, negative biopsy findings, and false immunolabeling of amyloid deposits were the main causes of diagnostic errors. We conclude that DNA testing, which is the most reliable test for TTR-FAP, should be performed in patients with a progressive length-dependent small fiber polyneuropathy of unknown origin, especially when associated with autonomic dysfunction.

[The diagnosis and management of familial amyloid polyneuropathy]. / Neuropathies amyloïdes familiales: diagnostic et prise en charge.

INTRODUCTION: Familial amyloid polyneuropathy designates a group of dominantly inherited neuropathies, with extracellular deposition of amyloid substance in various tissues. BACKGROUND: The 3 main precursor proteins encountered in these disorders are transthyretin, apolipoprotein A1 or gelsolin. Among them, transthyretin neuropathies are by far the most frequent type with a severe sensori-motor and autonomic neuropathy as the hallmark of the disease, most often associated with cardiac manifestations. First described in Portugal, the affection was subsequently reported across the world, although Portugal, Japan and Sweden are the 3 main areas of prevalence. In the past years, an increasing number of mutations have been identified in the TTR gene, along with a larger clinical spectrum than initially thought. Variable age of onset and penetrance are also largely reported with unclear phenotypic-genotypic correlations. Indeed, the contribution of the molecular genetics is important to ensure the diagnosis at an early stage, but also for predictive diagnosis, in the setting of genetic counselling. PERSPECTIVES: Over the last 15 years, liver transplantation (LT) has enabled improved prognosis of this devastating condition. FUTURE PROSPECTS: at present, such procedure should be performed in Val30Met patients, as early as possible in the course of the disease. Experience with such procedure in patients with other TTR variants remains scarce. Other therapeutic strategies are awaited. CONCLUSION: This review summarizes the recent data on the diagnosis and management of patients and families affected with TTR amyloid neuropathy.

Thymidine phosphorylase gene mutations in patients with mitochondrial neurogastrointestinal encephalomyopathy syndrome.

The mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) syndrome is characterized by the association of gastrointestinal and neurological symptoms. It is a rare autosomal recessive mitochondrial disorder with multiple mitochondrial DNA deletions and/or depletion. It is caused by thymidine phosphorylase (TP) gene mutations resulting in a complete abolition of TP activity. We tested 31 unrelated patients presenting either with a complete MNGIE syndrome (8 patients), a severe intestinal pseudo-obstruction (10 patients), and multiple deletions and/or depletion of mitochondrial DNA (13 patients). All the tested patients presenting with a complete MNGIE had increased thymidine levels in plasma and urine, and no TP activity. The group with pseudo-obstruction syndrome had normal or partial reduction of TP activity. We found pathogenic mutations on TP gene only in the MNGIE syndrome group: all the MNGIE patients were compound heterozygous or homozygous for mutations in the TP gene. Eight of these mutations are yet unreported, confirming the lack of genotype/phenotype correlation in this syndrome. Enzymatic activity and thymidine level are thus rapid diagnosis tests to detect MNGIE affected patients prior to genetic testing for patients with gastrointestinal symptoms.

The range of chronic demyelinating neuropathy of infancy: a clinico-pathological and genetic study of 15 unrelated cases.

The concept of Dejerine-Sottas disease, which corresponds to presumed recessive demyelinating neuropathies with onset in infancy, remains controversial. To learn more on the subject, we performed a clinico-pathological and molecular genetic study in 15 unrelated patients with the Dejerine-Sottas phenotype seen over a 16 year period. There were 12 females and 3 males, born to asymptomatic parents. Study of the PMP22, P0 and Egr2 genes was performed in all cases and 14 underwent a nerve biopsy. First manifestations of neuropathy occurred before 3 years of age in all patients. An inherited disorder was suspected in 10 patients, because of their family history and/or disclosure of a molecular genetic defect in 4 of them. One patient had a recessively transmitted homozygous point mutation (Arg157Trp) of the PMP22 gene. A heterozygous duplication of the 17p11.2-12 segment was detected in one offspring of a consanguineous marriage. One patient carried a "de novo" heterozygous Ser72Leu substitution in the PMP22. A heterozygous double mutation of the P0 gene including a "de novo" Val42 deletion and an Ala221Thr substitution, maternally inherited, were found in an apparently sporadic case. No mutation of the Egr2 gene was identified. A neuropathy with focally folded myelin sheaths (CMT4B) was diagnosed in the nerve biopsy specimens of two patients. In five patients, the clinico-pathological findings along with the absence of an identified mutation suggested the diagnosis of chronic inflammatory demyelinating polyneuropathy of infantile onset. Our findings illustrate the genetic heterogeneity of cases with identified mutations, the scarcity of cases with "demonstrated" recessive transmission and the likelihood of early acquired chronic inflammatory demyelinating polyneuropathy in several patients.

Transthyretin related familial amyloid polyneuropathy.

Familial amyloid polyneuropathy (FAP) applies to a group of dominantly inherited severe diseases with endoneurial and polyvisceral deposition of amyloidosis. The transthyretin, essentially produced by the liver, is the main protein involved in FAP. Up to 80 different mutations of the transthyretin gene are identified, many of them being associated with small fibres sensory-motor and autonomic polyneuropathy and/or cardiomyopathy. Variable age of onset, clinical expression and penetrance are largely reported. However, phenotypic-genotypic correlations remain unclear and the genetic or environmental modifying factors are unknown. The liver transplantation is proposed as a curative treatment of FAP resulting in an improvement of the general condition and a stabilization of the neuropathy, in a majority of patients. At present, the ratio benefit/risk seems acceptable when the procedure is performed early in the course of the disease.

The Roussy-Lévy family: from the original description to the gene.

In 1926, Roussy and Lévy described a large family whose members manifested an early onset dominantly inherited gait ataxia, pes cavus, and areflexia, which was eventually associated with distal muscle atrophy, postural tremor, and minor sensory loss. Slow nerve conduction and demyelination of nerve fibers with onion bulb formations in nerve biopsy specimens led to the Roussy-Lévy syndrome (RLS) being considered a variant of demyelinating Charcot-Marie-Tooth disease (CMT-1). In the present article, we report on the long-term follow-up, on nerve biopsy findings, and on the underlying molecular genetic defect in members of the original family studied by Roussy and Lévy. All patients were able to walk during their seventh decade of life. Morphologically, a chronic demyelinating neuropathy with the remarkable aspects of a focally hypertrophic myelin sheath and major loss of myelinated fibers was observed in nerve biopsy specimens of 3 members of this family. Molecular genetic testing identified a previously unknown heterozygous missense point mutation which yielded an Asn131Lys substitution in the extracellular domain of the myelin protein zero (P0). These findings show that the Roussy-Lévy family belongs to the CMT-1B subtype and has original morphological and genetic features.

Recessive inheritance of a new point mutation of the PMP22 gene in Dejerine-Sottas disease.

The existence of recessive transmission of Dejerine-Sottas disease, a severe demyelinating neuropathy of childhood, has been questioned, because only heterozygous mutations of the myelin proteins P0 or PMP22 genes have been identified in virtually all patients with this phenotype. We report on a family with 3 affected children with this phenotype, born to clinically and electrophysiologically unaffected parents. All 3 children carried a previously unknown homozygous missense point mutation (Arg157Trp) of the PMP22 gene. The parents were heterozygous for the same mutation. These findings demonstrate the occurrence of recessive transmission in this setting.

Marked systemic amyloid angiopathy in patients with val 107 transthyretin mutation.

We report three non-inbred patients with Val 107 transthyretin (TTR) amyloidosis. Clinical features were remarkable by the combination of peripheral polyneuropathy, carpal tunnel syndrome, cardiomyopathy, and epilepsy. Pathologic examination disclosed unusual striking systemic amyloid angiopathy in all studied tissues including nerve, muscle, gut, lung, salivary glands, and synovial membrane. It appears that the rare TTR Val 107 variant causes a peculiar familial amyloid syndrome characterized by both widespread systemic TTR amyloidosis and central nervous system deposition sufficient to cause seizures, pointing out the extent of TTR amyloidosis phenotypic heterogeneity.