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Contrast-induced acute kidney injury (CI-AKI) is a common cause of hospital-acquired acute kidney injury (AKI). We evaluated the evidence that uric acid (UA) plays a pathogenic role in CI-AKI. Ten studies were eligible for inclusion for meta-analysis. Hyperuricemia predicted risk for cases with AKI in prospective cohort studies. Higher levels of serum UA (SUA), as defined by the authors, were associated with a 2-fold increased risk to develop AKI (pooled odds ratio 2.03; 95% confidence interval [CI] 1.48-2.78). Significant heterogeneity was found in cohort studies ( P = .001, I = 85.7%). In 2 clinical trials, lowering of SUA with saline hydration was significantly associated with reduced risk for AKI compared with saline hydration alone or saline hydration with N-acetyl cysteine. An analysis of 2 randomized controlled trials found that allopurinol with saline hydration had a significant protective effect on renal function (assessed by serum creatinine values) compared with hydration alone (mean difference: -0.52 mg/dL; 95% CI: -0.81 to -0.22). Hyperuricemia independently predicts CI-AKI. Two clinical trials suggest lowering SUA may prevent CI-AKI. The mechanism by which UA induces CI-AKI is likely related to acute uricosuria.

Background: Mutations in the slow skeletal muscle troponin T (TNNT1) gene cause a congenital nemaline myopathy resulting in death from respiratory insufficiency in early infancy. We report on four French Canadians with a novel congenital TNNT1 myopathy. Methods: Patients underwent lower extremity and paraspinal MRI, quadriceps biopsy and genetic testing. TNNT1 expression in muscle was assessed by quantitative PCR and immunoblotting. Wild type or mutated TNNT1 mRNAs were co-injected with morpholinos in a zebrafish knockdown model to assess for rescue of the morphant phenotype. Results: Four patients shared a novel missense homozygous mutation in TNNT1. They developed from childhood slowly progressive limb-girdle weakness with spinal rigidity and contractures. They suffered from restrictive lung disease and recurrent episodes of rhabdomyolysis. Older patients remained ambulatory into their sixties. Lower extremity MRI showed symmetrical myopathic changes. Paraspinal MRI showed diffuse fibro-fatty involution. Biopsies showed multi-minicores. Nemaline rods were seen in half the patients. TNNT1 mRNA expression was similar in controls and patients, while levels of TNNT1 protein were reduced in patients. Wild type TNNT1 mRNA rescued the zebrafish morphants but mutant transcripts failed to do so. Conclusions: This study expands the spectrum of TNNT1-related myopathy to include a milder clinical phenotype caused by a functionally-confirmed novel mutation.

Objective Recessive null variants of the slow skeletal muscle troponin T1 (TNNT1) gene are a rare cause of nemaline myopathy that is fatal in infancy due to respiratory insufficiency. Muscle biopsy shows rods and fiber type disproportion. We report on 4 French Canadians with a novel form of recessive congenital TNNT1 core‐rod myopathy. Methods Patients underwent full clinical characterization, lower limb magnetic resonance imaging (MRI), muscle biopsy, and genetic testing. A zebrafish loss‐of‐function model using morpholinos was created to assess the pathogenicity of the identified variant. Wild‐type or mutated human TNNT1 mRNAs were coinjected with morpholinos to assess their abilities to rescue the morphant phenotype. Results Three adults and 1 child shared a novel missense homozygous variant in the TNNT1 gene (NM_003283.6: c.287T > C; p.Leu96Pro). They developed from childhood very slowly progressive limb‐girdle weakness with rigid spine and disabling contractures. They suffered from restrictive lung disease requiring noninvasive mechanical ventilation in 3 patients, as well as recurrent episodes of rhabdomyolysis triggered by infections, which were relieved by dantrolene in 1 patient. Older patients remained ambulatory into their 60s. MRI of the leg muscles showed fibrofatty infiltration predominating in the posterior thigh and the deep posterior leg compartments. Muscle biopsies showed multiminicores and lobulated fibers, rods in half the patients, and no fiber type disproportion. Wild‐type TNNT1 mRNA rescued the zebrafish morphants, but mutant transcripts failed to do so. Interpretation This study expands the phenotypic spectrum of TNNT1 myopathy and provides functional evidence for the pathogenicity of the newly identified missense mutation. ANN NEUROL 2020;87:568–583