Efficacy and Limitations of Corneal Confocal Microscopy in Evaluating ATTRv-PN.

OBJECTIVE: Driven by pathogenic variants in the TTR gene, hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) presents as a systemic autosomal dominant disorder. This cross-sectional study aimed to investigate the clinical utility of in vivo corneal confocal microscopy (CCM) for assessing structural changes in corneal nerve fibers among ATTRv-PN patients and presymptomatic carriers. METHODS: A total of 41 ATTRv-PN patients, 15 ATTRv-PN presymptomatic carriers, and 15 healthy controls underwent CCM assessment. Clinical neurological scores, electrophysiological data, and sural biopsy data from ATTRv-PN patients and carriers were analyzed. We calculated the corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), inferior whorl fiber length (IWFL), inferior whorl fiber density (IWFD), inferior whorl branch density (IWBD), corneal Langerhans cell density (CLCD), and inferior whorl Langerhans cell density (IWLCD). We compared the CCM parameters between patients, carriers, and healthy controls and analyzed their correlations with clinical, electrophysiological, and pathological changes in patients with ATTRv-PN. RESULTS: CCM parameters, including CNFL, CNFD, CNBD, IWFL, CLCD, and IWLCD, were abnormal in ATTRv-PN patients (p < 0.05). Statistical analysis revealed no significant variation in evaluated CCM parameters between the early-onset and late-onset ATTRv-PN patient subgroups. Similarly, there were not statistically significant differences in these parameters between Stage I patients and Stage II patients. All CCM parameters except CNFD and IWFL were abnormal in presymptomatic carriers (p < 0.05). The CNFL and IWLCD (p < 0.05) were correlated with disease duration. The CNFL, CNFD, and CNBD were positively correlated with sural large myelinated nerve fiber density (p < 0.05), so were CNFL and IWFL with the total myelinated nerve fiber density (p < 0.05) in the sural nerve. CONCLUSION: As an in vivo, noninvasive imaging technique, CCM facilitates the detailed evaluation of corneal nerve fiber morphology in both symptomatic ATTRv-PN individuals and asymptomatic mutation carriers. We have confirmed the significant abnormalities of CCM parameters of corneal nerve fibers in ATTRv-PN patients and presymptomatic carriers.