Natural course and determinants of short-term kidney function decline in hereditary transthyretin amyloidosis: a French observational study

Data regarding renal involvement in patients with hereditary transthyretin (ATTRv) amyloidosis are scarce and the natural course of chronic kidney disease (CKD) in this population remains unclear. This observational study, including adult patients diagnosed with ATTRv amyloidosis at the French Reference Centre for Cardiac Amyloidosis, investigated renal function outcome and its determinants. Multivariable logistic regression models identified factors associated with CKD at baseline. Determinants of the change in estimated glomerular filtration rate (eGFR) over 24 months of follow-up were assessed with a multivariable linear mixed-effects model. In total, 232 patients (78 women [34%], mean age: 64 years) with ATTRv amyloidosis were classified on the basis of their <i>TTR</i> variants: ATTRV122I (37%), ATTRV30M (29%), and other variants (34%). Median baseline eGFR was 78 ml/min/1.73 m². Seventy-two patients (31%) had an eGFR below 60 ml/min/1.73m² and 27/137 patients (20%) had significant proteinuria (urine protein/creatinine ratio ≥30 mg/mmol). Renal biopsy, performed in four cases, found typical Congo red-positive and TTR-labelled amyloid deposits in all cases. Older age (OR 1.07, <i>p</i> &lt; .001) and a prior history of hypertension (OR 2.09, <i>p</i> = .04) were associated with a higher prevalence of CKD at baseline, whereas higher left ventricular global longitudinal strain (LVGLS) (OR 0.83, <i>p</i> &lt; .001) was associated with a lower prevalence. The estimated change in eGFR was −7.12 [−9.61, −4.63] and −8.21 [−10.81, −5.60] ml/min/1.73 m² after 12 and 24 months of follow-up, respectively. eGFR decline was independently associated with older age ((67–74], coefficient= −14.35 mL/min/1.73 m², <i>p</i> &lt; .01, &gt;74, coefficient = −22.93 mL/min/1.73 m², <i>p</i> &lt; .001, versus &lt;56), ATTRV122I (coefficient = −17.17 mL/min/1.73m², <i>p</i> &lt; .01, versus ATTRV30M) and LVGLS (coefficient = 1.22, <i>p</i> &lt; .01). These data suggest that CKD is a common finding in patients with ATTRv amyloidosis, and that eGFR decline is rapid during the first year of evaluation. Older age, lower LVGLS and ATTRV122I were associated with a worse renal outcome. Further studies are now needed to evaluate effects of new targeted therapies on long term renal function.