A Novel Case of Nerve Biopsy Proven Wild Type Transthyretin (TTR) Amyloidosis

To report a novel case of biopsy-proven, mass spectrometry-confirmed, wild-type transthyretin amyloidosis (ATTRwt) in nerve.

The patient was identified and evaluated in the peripheral nerve clinic. Our nerve laboratory's pathology database and the literature were searched for prior evidence of pathologically confirmed cases of ATTRwt.

A 94-year-old man with a history of lumbar spinal stenosis presented to the neurology clinic with subacute-on-chronic progressive, upper limb predominant weakness along with numbness and tingling paresthesia. Electromyography (EMG) revealed multiple mononeuropathies involving the right median nerve at the wrist, right ulnar nerve, and right distal radial nerve superimposed upon an axonal predominant peripheral neuropathy along with multilevel lumbosacral radiculopathies. Extensive serology for causes of neuropathy and multiple mononeuropathies returned unremarkable. A diagnostic right superficial radial nerve biopsy was performed and showed congophilic material within a small epineurial vessel wall in the nerve tissue. Amyloid typing by mass spectrometry was performed and revealed ATTRwt. TTR gene sequencing returned normal. The patient was diagnosed with ATTRwt neuropathy and started on diflunisal therapy for neuropathy treatment.

This case confirms the presence of ATTRwt deposition directly in nerve tissue as the likely cause of the patient's large fiber and multiple mononeuropathies, expanding our current understanding of ATTRwt-associated disease. Proving the direct association of ATTRwt and neuropathy may open up amyloid-specific treatments for this disease.