Clinical and genetic characters of 8 Chinese children with ADCK4-associated glomerulopathy

Abstract

Objective To investigate the clinical and genetic character of Chinese children with the aarF domain containing kinase 4 (ADCK4)-associated glomerulopathy. Methods Applying next generation sequencing to detect possible gene mutation(renal disease associated monogene was pooled as one panel) in 69 children with steroid-resistant nephrotic syndrome (SRNS) or persistent proteinuria of unknown origin. Sanger sequencing was used to confirm the significant mutations found in the children and to validate these mutation sites in their patients. Using online software (PolyPhen2, SIFT, Mutation Taster) to predict whether the detected missense mutations were disease causing or not. Collecting and analyzing clinical data of children with ADCK4-associated glomerulopathy, which included onset age, clinical manifestation, and renal pathology. Results The ADCK4 gene mutation was detected in 8 children with a positive rate of 11.6% (8 out of 69), among which 3 patients carried homozygous c.748G>C mutation, 3 patients carried homologous c.737G>A mutation, 1 patient carried compound heterozygous mutation(c.748G>C and c.737G>A), and 1 patient carried compound heterologous mutation(c.551A>G and c.737G>A). Collectively, there were only 3 mutation sites found in total 8 patients, in which the mutation sites of c.748G>C and c.737G>A had high detection frequency in these 8 patients. These 3 mutation sites were all missense mutation which were predicted to be disease causing by online software and not reported before. The average onset age was 6.5 years (2 years-11.75 years). Four patients presented with SRNS and the other 4 presented with persistent proteinuria. All 8 patients had no extrarenal manifestation, renal biopsy revealed focal segmental glomerulosclerosis (FSGS) in most patients, among which 3 cases had gone to end-stage renal disease (ESRD) at disease onset, and 2 cases progressed to ESRD 2 and 5 years after onset respectively. Seven patients had received glucocorticoid and/or immunosuppressive drug while only one patient getting partial response. All 8 patients were treated with large amount of coenzyme Q10 (15 mg·kg-1·d-1) after definite diagnosis of ADCK4 mutation-some patients had acquired encouraging curative effect. Conclusions ADCK4-associated glomerulopathy is not rare especially in the children with SRNS. The onset age is relatively old and the extrarenal manifestation is less common. FSGS is a main pathology type. Patients usually have no response to immunosuppressive therapy, but may benefit from addition of large amount of coenzyme Q10. Some patients may only manifest with insidious proteinuria, causing the early diagnosis to be difficult, which deserves more attention. Three new missense mutations expand disease causing mutation repertoire of ADCK4 gene, among which the two sites of c.748G>C and c.737G>A may be mutation hotspot of ADCK4-associated glomerulopathy in Chinese population, and need further study. Key words: Nephrotic syndrome; Proteinuria; Mutation; Ubiquinone; AarF domain containing kinase 4