Variable presentations of TTR-related familial amyloid polyneuropathy in seventeen patients

Description of transthyretin S50A, S52P and G47A mutations in familial amyloidosis polyneuropathy

OBJECTIVE

To describe 58 subjects with rare TTR mutations, and to compare the different biomarkers between carriers and patients.

METHODS

TTR gene sequence test was performed in 15 suspicious subjects and in their direct family. All positive subjects undertook prospective evaluations in a period of 49 months.

RESULTS

Of 95 genetic tests performed, 58 (61%) were positive for TTR mutations, Ser50Arg mutation in 38 (65%), Ser52Pro in 15 (26%) and Gly47Ala in 5 (9%). Initial symptoms were neuropathic in 19 (73%), gastrointestinal in 6 (23%) and autonomic in 1 (4%).

CONCLUSIONS

The natural history of Ser50Arg, Ser52Pro and Gly47Ala TTR mutations is similar to the Val30Met mutation described in endemic areas. The small fiber assessments were the initial tests to show abnormalities in asymptomatic subjects.

Diagnostic hallmarks and pitfalls in late-onset progressive transthyretin-related amyloid-neuropathy

Familial amyloid polyneuropathy (FAP) is a progressive systemic autosomal dominant disease caused by pathogenic mutations in the transthyretin (TTR) gene. We studied clinical, electrophysiological, histopathological, and genetic characteristics in 15 (13 late-onset and two early-onset) patients belonging to 14 families with polyneuropathy and mutations in TTR. In comparison, we analysed the features of nine unrelated patients with an idiopathic polyneuropathy, in whom TTR mutations have been excluded. Disease occurrence was familial in 36 % of the patients with TTR-associated polyneuropathy and the late-onset type was observed in 86 % (mean age at onset 65.5 years). Clinically, all late-onset TTR-mutant patients presented with distal weakness, pansensory loss, absence of deep tendon reflexes, and sensorimotor hand involvement. Afferent-ataxic gait was present in 92 % leading to wheelchair dependence in 60 % after a mean duration of 4.6 years. Autonomic involvement was observed in 60 %, and ankle edema in 92 %. The sensorimotor polyneuropathy was from an axonal type in 82 %, demyelinating or mixed type in 9 % each. Compared to the TTR-unmutated idiopathic polyneuropathy patients, we identified rapid progression, early ambulatory loss, and autonomic disturbances, associated with a severe polyneuropathy as red flags for TTR-FAP. In 18 % of the late-onset TTR-FAP patients, no amyloid was found in nerve biopsies. Further diagnostic pitfalls were unspecific electrophysiology, and coincident diabetes mellitus (23 %) or monoclonal gammopathy (7 %). We conclude that a rapid disease course, severely ataxic gait, hand involvement, and autonomic dysfunction are diagnostic hallmarks of late-onset TTR-FAP. Genetic analysis should be performed even when amyloid deposits are lacking or when polyneuropathy-causing comorbidities are concomitant.

An amyotrophic lateral sclerosis-like syndrome revealing an amyloid polyneuropathy associated with a novel transthyretin mutation

OBJECTIVE

Familial amyloid polyneuropathy (FAP) is typically a predominantly sensory and autonomic neuropathy with progressive and late motor involvement leading to death within 10 years. Recently, prognosis was transformed with liver transplantation.

METHODS

We report an atypical sporadic pure motor and bulbar neuropathy initially mistaken for amyotrophic lateral sclerosis (ALS) in a 50-year-old Malian man.

RESULTS

The diagnostic procedure of this clinical purely motor and bulbar neuropathy disclosed amyloid deposits on nerve biopsy which led to the identification of a new Val93Met mutation of transthyretin. This case was also remarkable by its slow progression.

CONCLUSIONS

This report confirms the motor phenotype of TTR-FAP. That should be considered in the differential diagnosis of motor neuron diseases in order to start accurate therapy.

Effect on disability and safety of Tafamidis in late onset of Met30 transthyretin familial amyloid polyneuropathy

BACKGROUND AND PURPOSE

The aim of this study was to assess the effect of Tafamidis, which slows the progression of early stages of Met30 transthyretin (TTR) familial amyloidosis polyneuropathy (FAP) in more advanced cases.

METHODS

The study was a prospective, non-randomized controlled trial carried out at the French national reference centre for FAP with follow-up at 1 year. Thirty-seven consecutive Met30-TTR-FAP patients were enrolled between December 2009 and July 2011, with NIS-LL (Neuropathy Impairment Score-lower limbs) > 10 and Karnofsky score > 60. Their mean (SD) age was 56.4 (19) years. Seventy-seven per cent of patients had a walking disability. Seven patients (19%) were withdrawn for adverse effects. The primary study outcome measurements, planned before data collection began, were NIS-LL and NIS-UL (upper limbs) scores and disability scores.

RESULTS

Of the 37 patients entered into the study, 29 were evaluated at 6 months and 13 at 12 months. During the first 6 months of treatment, the mean progression of NIS-LL score was 4.8 and was similar to that during the period before treatment. Among the 45% of patients without NIS-LL progression, the NIS-UL score worsened in 55%. During the first year, 55% deteriorated with respect to disability and 38% with respect to NIS only; only two patients (7%) remained stable. Four (out of 20; 20%) patients who were previously stage 1 reached stage 2 (walking with aid) after this period. Two out of nine patients who were initially normotensive developed orthostatic hypotension. There were a total of 19 adverse events, including four febrile urinary tract infections and three severe diarrhoeas, with faecal incontinence in two.

CONCLUSION

In most patients with advanced Met30 TTR-FAP, Tafamidis is not able to stop disease progression, in respect of both NIS-LL and disability. Other anti-amyloid medicines should be assessed in this context.

Familial amyloidotic polyneuropathy: current and emerging treatment options for transthyretin-mediated amyloidosis

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a fatal clinical disorder characterized by extracellular deposition of abnormal fibrils derived from misfolded, normally soluble transthyretin (TTR) molecules. The disease is most commonly caused by a point mutation within the TTR gene inherited in an autosomal dominant fashion. Over 100 of such mutations have been identified, leading to destabilization of the physiological TTR tetramer. As a result, many monomers originate with a tendency for spontaneous conformational changes and self-aggregation. The main clinical feature of TTR-FAP is progressive sensorimotor and autonomic neuropathy. In the beginning, this polyneuropathy predominantly involves small unmyelinated nerve fibers with the result of dissociated sensory loss disproportionately affecting sensation of pain and temperature. Autonomic neuropathy typically accompanies sensory deficits early in the disease course. The symptoms include orthostatic hypotension, constipation alternating with diarrhea, erectile dysfunction, anhydrosis, and urinary retention or incontinence. Later, involvement of motor fibers causes rapidly progressive weakness and gait disturbances. In addition to the peripheral nervous system, the heart and the gut are frequently affected. Onset of symptoms is bimodal, with one peak at age 33 years (early onset) and another distinct peak in the sixth decade of life (late onset). The course of TTR-FAP is uniformly progressive and fatal. Death occurs an average of 10.8 years after the onset of symptoms in Portuguese patients, and 7.3 years in late-onset Japanese patients. Common causes include cachexia, cardiac failure, arrhythmia, and secondary infections. Liver transplantation is the standard therapy for patients who are in a clinical condition good enough to tolerate this intervention because it stops progression of neuropathy by removing the main source of mutant TTR. Recently, orally administered tafamidis meglumine has been approved by European authorities for treatment of FAP. The substance has been shown to stabilize the TTR tetramer, thereby improving the outcome of patients with TTR-FAP. Various other strategies have been studied in vitro to prevent TTR amyloidosis, including gene therapy, immunization, dissolution of TTR aggregates, and free radical scavengers, but none of them is ready for clinical use so far.

Two siblings diagnosed to have transthyretin-related familial amyloid cardiomyopathy around the same time at different hospitals

Mutation in the transthyretin (TTR) gene may clinically manifest as cardiomyopathy. Here, we describe 69-year-old and 72-year-old brothers who were diagnosed as having TTR-related familial amyloid cardiomyopathy by endomyocardial biopsy at different hospitals at around the same time. They were not from an endemic area of familial amyloid polyneuropathy. Genetic analysis showed a base change in the TTR gene leading to a p.Val30Met mutation in both patients. Screening of family members, as well as detailed family history taking, is important for the diagnosis of cardiomyopathy of unknown etiology.