Kidney Injury: An Overlooked Manifestation in Autoimmune Encephalitis

Aim: To investigate the prevalence and clinical features of kidney injury in patients with autoimmune encephalitis (AE).

Methods: Kidney injury was suspected in kidney-involving group due to persistent abnormal in urinary protein and serum albumin. Data on demographics and clinical features were compared between kidney-involving group and kidney-sparing group (patients without kidney injury) using Wilcoxon rank-sum test or chi-square test. Renal biopsy was conducted to identify the type of kidney injury.

Results: Approximate 30 % (32 of 108) patients with AE were suspicious of kidney injury. Nine patients further tested 24 h urine total protein, and seven of them had an elevated urine protein higher than 150 mg. The predominantly patterns of kidney injury were elevated urine protein, decreased serum albumin and normal kidney function. Compared to kidney-sparing group, the spectrum of AE antibodies in kidney-involving group was different, manifested as less anti-N-methyl-d-aspartate receptor antibodies (50 % vs. 72.4 %, p = 0.025) and more anti-contactin-associated protein like 2 antibodies (18.8 % vs. 1.3 %, p = 0.003). Definite pathological changes indicative of IgA nephropathy and membranous nephropathy in renal biopsy of two cases provided evidence of autoimmune attacks.

Discussion: Kidney injury occurred in considerable proportion of patients with AE. An in-depth screening for nephropathy could be essential for AE.