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Abstract
Objective To clearly define transthyretin familial amyloid polyneuropathies (TTR-FAPs) fulfilling definite clinical and electrophysiologic European Federation of Neurological Societies/Peripheral Nerve Society criteria for chronic inflammatory demyelinating polyneuropathy (CIDP).
Methods From a cohort of 194 patients with FAP, 13 of 84 patients (15%) of French ancestry had late-onset demyelinating TTR-FAP. We compared clinical presentation and electrophysiology to a cohort with CIDP and POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes) syndrome. We assessed nerve histology and the correlation between motor/sensory amplitudes/velocities. Predictors of demyelinating TTR-FAP were identified from clinical and electrophysiologic data.
Results Pain, dysautonomia, small fiber sensory loss above the wrists, upper limb weakness, and absence of ataxia were predictors of demyelinating TTR-FAP (p < 0.01). The most frequent demyelinating features were prolonged distal motor latency of the median nerve and reduced sensory conduction velocity of the median and ulnar nerves. Motor axonal loss was severe and frequent in the median, ulnar, and tibial nerves (p < 0.05) in demyelinating FAP. Ulnar nerve motor amplitude <5.4 mV and sural nerve amplitude <3.95 μV were distinguishing characteristics of demyelinating TTR-FAP. Nerve biopsy showed severe axonal loss and occasional segmental demyelination-remyelination.
Conclusion Misleading features of TTR-FAP fulfilling criteria for CIDP are not uncommon in sporadic late-onset TTR-FAP, which highlights the limits of European Federation of Neurological Societies/Peripheral Nerve Society criteria. Specific clinical aspects and marked electrophysiologic axonal loss are red flag symptoms that should alert to this diagnosis and prompt TTR gene sequencing.
Glossary
- AUC=
- area under the curve;
- CI=
- confidence interval;
- CIDP=
- chronic inflammatory demyelinating polyneuropathy;
- CMAP=
- compound muscle action potential;
- dFAP=
- demyelinating familial amyloid polyneuropathy;
- EFNS/PNS=
- European Federation of Neurological Societies/Peripheral Nerve Society;
- FAP=
- familial amyloid polyneuropathy;
- MCV=
- motor conduction velocity;
- POEMS=
- polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes;
- RR=
- relative risk;
- SCV=
- sensory conduction velocity;
- SNAP=
- sensory nerve action potential;
- TTR=
- transthyretin
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received November 30, 2017.
- Accepted in final form April 9, 2018.
- © 2018 American Academy of Neurology
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