Are pharmacological treatments for familial amyloid polyneuropathy effective and safe? A Cochrane Review summary with commentary

BACKGROUND: Familial amyloid polyneuropathies (FAPs) are a group of rare autosomal dominant transmitted disorders that can progressive lead to disability from neuropathy, autonomic failure and other system involvement. OBJECTIVE: The aim of this commentary is to discuss Cochrane evidence on the efficacy and safety of disease-modifying drugs (DMDs) for the treatment of FAPs from a rehabilitation perspective. METHODS: To summarize and discuss from a rehabilitation perspective the published Cochrane Review “Pharmacological treatment for familial amyloid polyneuropathy” by Magrinelli et al. RESULTS: This Cochrane review included 4 randomized controlled trials (RCTs) involving 655 adults with FAP. These four trials compared four different DMDs with placebo. The Cochrane Systematic Review reported that current evidence is limited. CONCLUSIONS: FAPs are a group of chronic disabling conditions in which a multidisciplinary approach, including an adequate rehabilitation programme along with a long-term effective pharmacological therapy, should always be envisaged.

Transthyretin Misfolding, A Fatal Structural Pathogenesis Mechanism

Transthyretin (TTR) is an essential transporter of a thyroid hormone and a holo-retinol binding protein, found abundantly in human plasma and cerebrospinal fluid. In addition, this protein is infamous for its amyloidogenic propensity, causing various amyloidoses in humans, such as senile systemic amyloidosis, familial amyloid polyneuropathy, and familial amyloid cardiomyopathy. It has been known for over two decades that decreased stability of the native tetrameric conformation of TTR is the main cause of these diseases. Yet, mechanistic details on the amyloidogenic transformation of TTR were not clear until recent multidisciplinary investigations on various structural states of TTR. In this review, we discuss recent advancements in the structural understanding of TTR misfolding and amyloidosis processes. Special emphasis has been laid on the observations of novel structural features in various amyloidogenic species of TTR. In addition, proteolysis-induced fragmentation of TTR, a recently proposed mechanism facilitating TTR amyloidosis, has been discussed in light of its structural consequences and relevance to acknowledge the amyloidogenicity of TTR.

Nerve Ultrasound Comparison Between Transthyretin Familial Amyloid Polyneuropathy and Chronic Inflammatory Demyelinating Polyneuropathy

Backgrounds: Transthyretin familial amyloid polyneuropathy (TTR-FAP) is frequently misdiagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP) because of similar phenotypes in the two diseases. This study was intended to identify the role of nerve ultrasonography in evaluating TTR-FAP and CIDP.Methods: Eighteen patients with TTR-FAP, 13 patients with CIDP, and 14 healthy controls (HC) were enrolled in this study. Consecutive ultrasonography scanning was performed in six pairs of nerves of bilateral limbs with 30 sites. The cross-sectional areas (CSAs) and CSA variability data of different groups were calculated and compared.Results: Both TTR-FAP and CIDP showed larger CSAs at most sites of both upper and lower limbs than in HC groups. CIDP patients had larger CSAs than TTR-FAP patients at 8/15 of these sites, especially at U1-3, Sci2 sites (p < 0.01). However, the CSAs at above sites were not a credible index to differentiate TTR-FAP from CIDP with a low area under the curve (<0.8). The CSA variability of median nerves was significantly higher in CIDP than in TTR-FAP and HC groups, with high sensitivity (0.692) and specificity (0.833) to differentiate CIDP from TTR-FAP. The CSA variability of ulnar nerves was not significantly different between the three groups. For the TTR-FAP group, mean CSAs at each site were not correlated with different Coutinho stages, modified polyneuropathy disability, course of sensory motor peripheral neuropathy, Neuropathy Impairment Score, or Norfolk Quality of life-diabetic neuropathy score. The mean compound muscle action potential of ulnar nerves was negatively correlated with the mean CSAs of ulnar nerves.Interpretation: TTR-FAP patients had milder nerve enlargement with less variability in CSAs of median nerves than those with CIDP, suggesting that nerve ultrasound can be a potential useful auxiliary tool to help differentiate the two neuropathies.