Clinical and apparative investigation of large and small nerve fiber impairment in mixed cohort of ATTR-amyloidosis: impact on patient management and new insights in wild-type

Abstract

Introduction Neuropathy in transthyretin (ATTR) amyloidosis is frequently underdiagnosed, delaying effective treatment. Early detection of large- and small-nerve fiber damage via a comprehensive diagnostic algorithm impacts on clinical management. Methods A mixed cohort of patients with ATTR amyloidosis (wild type-wt, hereditary-v and TTR gene mutation carriers) of the Interdisciplinary Amyloidosis Centre of Northern Bavaria underwent clinical examination, nerve conduction studies (NCS), quantitative sensory testing (QST), sympathetic skin response (SSR), quantitative sudomotor axon reflex testing (QSART), and skin punch biopsies. Results Out of 30 study participants (7 ATTRv/asymptomatic gene carriers, 23 ATTRwt) large-fiber neuropathy was found in 43% patients with ATTRv and 70% with ATTRwt. QST revealed a mixed small and large fiber impairment in all ATTRv/asymptomatic gene carriers and in 78% of ATTRwt. Autonomic tests were pathological in the majority of ATTRv and over 50% of ATTRwt patients. Skin biopsies (sampled from 19 patients) showed reduced intraepidermal nerve fiber density (IENFD) in all ATTRv/asymptomatic gene carriers and over 80% of ATTRwt. Two ATTRwt patients had a pure small fiber neuropathy. After reviewing for relevant co-morbidities, 44% of ATTRwt patients exhibited neuropathy (large and/or small fiber) without evidence of any other underlying cause. Disease manifestation in the peripheral nervous system was newly diagnosed in three ATTR gene mutation carriers, thereby influencing clinical management. Conclusion This comprehensive test program gives new insights regarding the presence of neuropathy in ATTRv and ATTRwt, which impact on patient management.