Inherited kidney diseases are the fifth most common cause of end-stage renal disease (ESRD). Mitochondrial dysfunction plays a vital role in the progression of inherited kidney diseases, while mitochondrial-transfer RNA (mt-tRNA) variants and their pathogenic contributions to kidney disease remain largely unclear. In this study, we identified the pathogenic mt-tRNA ^Phe 616T>C mutation in 3 families and documented that m.616T>C showed a high pathogenic threshold, with both heteroplasmy and homoplasmy leading to isolated chronic kidney disease and hyperuricemia without hematuria, proteinuria, or renal cyst formation. Moreover, 1 proband with homoplamic m.616T>C presented ESRD as a child. No symptoms of nervous system evolvement were observed in these families. Lymphoblast cells bearing m.616T>C exhibited swollen mitochondria, underwent active mitophagy, and showed respiratory deficiency, leading to reduced mitochondrial ATP production, diminished membrane potential, and overproduction of mitochondrial ROS. Pathogenic m.616T>C abolished a highly conserved base pair (A31-U39) in the anticodon stem-loop which altered the structure of mt-tRNA ^Phe , as confirmed by a decreased melting temperature and slower electrophoretic mobility of the mutant tRNA. Furthermore, the unstable structure of mt-tRNA ^Phe contributed to a shortage of steady-state mt-tRNA ^Phe and enhanced aminoacylation efficiency, which resulted in impaired mitochondrial RNA translation and a significant decrease in mtDNA–encoded polypeptides. Collectively, these findings provide potentially new insights into the pathogenesis underlying inherited kidney disease caused by mitochondrial variants.

Background. Both Lowe syndrome and Dent-2 disease are caused by variants in the OCRL gene. However, the reason why patients with similar OCRL gene mutations presented with different phenotypes remains uncertain. Methods. Children with hemizygous pathogenic or likely pathogenic variants in OCRL were compiled from published and unpublished consecutive cases from China. Furthermore, a Chi-square test was employed to analyze the correlation of the location and types of mutations on the phenotype of children with Lowe syndrome or Dent-2 disease. Results. Among the total 83 patients, 70.8% (34/48) cases of Lowe syndrome presented with truncating mutations, while only 31.4% (11/35) cases of Dent-2 disease presented with truncating mutation (Χ² = 12.662; ). Meanwhile, the majority of mutations in Dent-2 disease are located in Exon 2–12 (21/35, 60.0%), while the majority of mutations in Lowe syndrome are located in Exon 13–23 (39/48, 81.3%; Χ² = 14.922; ). Conclusions. Truncating mutations of the OCRL gene were more common in patients with Lowe syndrome than in Dent-2 disease, while mutation is more likely located at exon 2–12 in Dent-2 disease than that in Lowe syndrome. The type and location of mutation are important indicators for the phenotypes in patients with OCRL mutation. This is a large cohort study analyzing the genotype-phenotype correlation in patients with Lowe syndrome and Dent-2 disease in China. Our data may improve the interpretation of new OCRL variants and genetic counseling. Furthermore, a large international study would be necessary to illustrate the genotype-phenotype correlation in patients with OCRL mutations.

Fanconi syndrome is one of the primary renal manifestations of mitochondrial cytopathies caused by mitochondrial DNA (mtDNA) mutation. The common 4977-bp mtDNA deletion has been reported to be associated with aging and diseases involving multiple extrarenal organs. Cases of Fanconi syndrome caused by the 4977-bp deletion were rarely reported previously. Here, we report a 6-year-old girl with growth retardation in the course of Fanconi syndrome. She had mild ptosis and pigmented retinopathy. Abnormal biochemical findings included low-molecular-weight proteinuria, normoglycemic glycosuria, increased urine phosphorus excretion, metabolic acidosis, and hypophosphatemia. Growth records showed that her body weight and height were normal in the first year and failed to thrive after the age of three. Using a highly sensitive mtDNA analysis methodology, she was identified to possess the common 4977-bp mtDNA deletion. The mutation rate was 84.7% in the urine exfoliated cells, 78.67% in the oral mucosal cells, and 23.99% in the blood sample. After three months of oral coenzyme Q10 and levocarnitine treatment in combination with standard electrolyte supplement, her condition was improved. This is a report of growth retardation as the initial major clinical presentation of Fanconi syndrome caused by the deletion of the 4977-bp fragment. Renal tubular abnormality without any other extrarenal dysfunction may be an initial clinical sign of mitochondrial disorders. Moreover, considering the heterogeneity of the phenotypes associated with mtDNA mutations, the risk of developing Kearns–Sayre syndrome (KSS) with age in this patient should be noted because she had ptosis, retinal involvement, and changes in the brain and skeletal muscle.

Background: Fabry disease (FD) is an X-linked lysosomal storage disorder caused by GLA mutations, leading to deficient α-galactosidase A (α-Gal A) activity and progressive glycosphingolipid accumulation. While α-Gal A activity is the diagnostic gold standard, its sensitivity is reduced in late-onset or heterozygous patients. Conventional biomarkers such as lyso-Gb3 provide only limited insight into disease progression and therapeutic response. Exosomes, as stable carriers of disease-specific proteins, may offer complementary biomarkers for early detection and longitudinal monitoring. Methods: Twenty-one pediatric FD patients with confirmed GLA mutations were enrolled. Clinical, enzymatic, renal, and cardiac parameters were assessed. Plasma-derived exosomes were characterized by transmission electron microscopy and proteomic profiling. Differentially expressed proteins were identified using mass spectrometry, analyzed using GO/KEGG enrichment, and validated using RT-PCR, ELISA, and immunofluorescence in patient samples and Gla^−/− mice. Results: Male patients showed markedly reduced α-Gal A activity and elevated lyso-Gb3 compared with females. Although overt renal and cardiac dysfunction was uncommon, several patients exhibited early abnormalities such as proteinuria, an elevated LVMI, or increased cTnI levels. Proteomic analysis identified 2553 proteins, of which 188 were differentially expressed. Fibrosis- and inflammation-related proteins, including THBS1 and CFHR5, were upregulated, while protective factors such as APM1, SERPINA10, and CAB39 were downregulated. IGFBP3 was also elevated and closely linked to tissue remodeling. Enriched pathways were involved in PPAR/AMPK signaling, lipid metabolism, and complement activation. Conclusions: Exosomal proteomic profiling revealed early molecular signatures of cardiorenal involvement in pediatric FD. Key proteins such as THBS1, CFHR5, IGFBP3, APM1, and CAB39 show strong potential as biomarkers for risk stratification, disease monitoring, and therapeutic evaluation.