Transthyretin gene mutations in British and French patients with amyloid neuropathy

Renal amyloidosis: an update on diagnosis and pathogenesis

Amyloidosis is a diverse group of protein conformational disorder which is caused by accumulation and deposition of insoluble protein fibrils in vital tissues or organs, instigating organ dysfunction. Renal amyloidosis is characterized by the acellular Congo red-positive pathologic deposition of amyloid fibrils within glomeruli and/or the interstitium. It is generally composed of serum amyloid A-related protein or an immunoglobulin light chain; other rare forms lysozyme, gelsolin, fibrinogen alpha chain, transthyretin, apolipoproteins AI/AII/AIV/CII/CIII; and the recently identified form ALECT2. This disease typically manifests with heavy proteinuria, nephrotic syndrome, and finally progression to end-stage renal failure. Early diagnosis of renal amyloidosis is arduous as its symptoms appear in later stages with prominent amyloid deposition. The identification of the correct type of amyloidosis is quite troublesome as it can be confused with another related form. Therefore, the exact typing of amyloid is essential for prognosis, treatment, and correct management of renal amyloidosis. The emanation of new techniques of proteomic analysis, for instance, mass spectroscopy/laser microdissection, has provided greater accuracy in amyloid typing. This in-depth review emphasizes on the clinical features, renal pathological findings, and diagnosis of the AL and non-AL forms of renal amyloidosis.

The frequency of central nervous system complications in the Cypriot cohort of ATTRV30M neuropathy transplanted patients

BACKGROUND

Hereditary transthyretin amyloidosis (ATTR) is a hereditary, sensorimotor and autonomic neuropathy caused by deposits of mutated transthyretin (TTR). The commonest TTR mutation is V30M (ATTRV30M) with patients usually living for about 10 years after disease onset. Liver transplantation (LT) until recently was considered the standard treatment.

OBJECTIVE AND METHODS

This study aims to assess the frequency of CNS complications in post-LT patients from the Cypriot cohort. Epidemiological data were collected for all genetically confirmed ATTRV30M neuropathy patients diagnosed at CING since 1992, and CNS-associated symptoms were assessed and evaluated by two neurology specialists.

RESULTS

Out of the 48 transplanted patients, 10 (20.8%) presented with a CNS complication. All patients had ocular involvement, mainly glaucoma (7/10). Eight presented with transient focal neurological episodes (TFNEs), with expressive dysphasia being reported by four of them. The mean time of TFNE-emergence was 16.6 years after the LT. Three died from cerebral hemorrhage.

CONCLUSIONS

CNS complications in post-LT ATTRV30M patients are not rare and usually manifest themselves at a time that surpasses the mean time the patients would have survived without a LT. CNS involvement is associated with increased mortality, due to cerebral hemorrhage.

Professor P. K. Thomas: clinician, investigator, editor and leader--a retrospective appreciation

P. K. Thomas (1926-2008) occupied a prominent place in British and world neurology during the second half of the 20th century. Here, his lasting achievements as clinical neurologist, clinician scientist and experimentalist, editor of monographs and journals and leader of professional developments in the UK and elsewhere are assessed.

Extended phenotype in the transthyretin Tyr77 familial amyloid polyneuropathy

The transthyretin Tyr77 variant of familial amyloid polyneuropathy (FAP) has been identified in a few North American and European patients, but the full spectrum of its clinical manifestations is still not known. We report a 3-generation family of Jewish-Yemenite origin with Tyr77 FAP presenting with atypical features. The affected individuals had sensorimotor and autonomic neuropathy and cardiomyopathy accompanied by prominent dysphagia, hearing loss and asymptomatic carpal tunnel syndrome. Brain MRI in the proband showed multifocal white matter lesions. These features extend the reported Tyr77 phenotype and support the modifying effect of additional factors on the disease expression.

Clinical variant of familial amyloid polyneuropathy

Hereditary amyloidosis with early and prominent peripheral nerve involvement is often designated familial amyloid polyneuropathy (FAP). The abnormality usually lies in the transthyretin (TTR) gene. We describe a patient with a tyr77 TTR gene mutation who presented with sensorimotor polyneuropathy but no other systemic symptoms of amyloidosis. This is one of a few documented cases of the tyr77 mutation in North America. The clinical and electrophysiologic features of this unusual cause of sensorimotor polyneuropathy are discussed.

Transthyretin Tyr77 familial amyloid polyneuropathy: a clinicopathological study of a large kindred

More than 40 point mutations (producing different clinical manifestations) have been described in diverse points of the plasma protein transthyretin (TTR). The Met30 is considered the most common mutation, the Tyr77 mutation being the second most prevalent. However, data from patients with this late mutation are scarce, and usually come from isolated case reports or tables. The Tyr77 mutation is not as well characterized as the Met30 mutation, especially with respect to such aspects as prognosis or possible treatment by liver transplantation. We therefore present the clinical and pathological features of an extensive family with the Tyr77 TTR mutation, comprising 12 affected individuals over four generations. Six living individuals were followed over a 10-year period. Retrospective data were obtained with regard to the deceased family members. We found that an initial and sometimes prolonged carpal tunnel syndrome, beginning between the 6th and 7th decades, characterizes the Tyr77 mutation. In most cases this evolved to generalized peripheral nerve involvement, restrictive cardiomyopathy, and intestinal malabsortion. Although survival is usually high, there are progressive cases that should be candidates for liver transplant, before severe impairment has developed.

Peripheral nerve amyloidosis

Peripheral nerve amyloidosis is the cardinal feature of familial amyloid polyneuropathy (FAP) but can also be seen in primary light chain (AL) amyloidosis and dialysis (beta 2-microglobulin) related amyloidosis. The generalized neuropathy seen in all forms of peripheral nerve amyloidosis is similar, characterized by a severe progressive mixed neuropathy with autonomic dysfunction. Pathologically, amyloid is found in the peripheral nervous system as amorphous, eosinophilic, extracellular deposits. FAP is most commonly associated with variant plasma transthyretin (TTR), although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now at least 36 point mutations in the TTR gene associated with FAP and these continue to be described. Recent studies on the possible role individual point mutations in the TTR gene may play in amyloidosis have helped give us an insight into the mechanisms behind peripheral nerve amyloidosis. This article reviews the clinical and pathological features of the peripheral nerve amyloidosis and discusses theories of amyloidogenesis based on studies of FAP.

Haplotype analysis of French, British and other European patients with familial amyloid polyneuropathy (met 30 and tyr 77)

Familial amyloid polyneuropathy (FAP) is an autosomal dominant disorder originally and most frequently described in Portugal. The usual constituent amyloid fibril protein is transthyretin (TTR) and the most frequent mutation in the TTR gene associated with FAP (including all Portuguese cases) is that at position 30 (met 30). Three different TTR haplotypes have been described in association with the met 30 mutation in European patients. We studied the haplotypes of 27 families (24 French, 2 British and 1 Greek) with FAP met 30 by analysing three polymorphisms in introns of the TTR gene. We also studied 6 families (2 British, 3 French and 1 Spanish) with FAP tyr 77. There were two main haplotypes in French patients with FAP met 30, one most commonly seen in the French families of Portuguese descent which was the same haplotype as previously described in Portuguese patients (haplotype I) and another haplotype (III) detected in most informative French families not of Portuguese origin. The age of onset of symptoms was consistently later in French than in Portuguese patients and in patients with haplotype III as the disease-associated haplotype rather than haplotype I. British and French patients with the tyr 77 mutation had different haplotypes. The most likely explanation of these findings is multiple founders of both mutations.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathy (FAP) is most commonly associated with variant plasma transthyretin, although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now approximately 26 point mutations in the transthyretin gene associated with FAP. Because of the overlapping clinical phenotypes described with these mutations, it is now more appropriate to classify the various forms of FAP according to the underlying genetic defect rather than on clinical grounds. Many questions concerning the amyloidogenic nature of transthyretin and the variability of organ involvement depending on the underlying mutation remain unanswered. The recent use of liver transplantation for treatment appears to be promising.