Yuji Matsumoto

BACKGROUND: Proximal renal tubular dysfunction occurs during diabetic ketoacidosis (DKA) in type 1 diabetes. However, only a few studies have reported on the multiple proximal renal tubular functions simultaneously. Moreover, to the best of our knowledge, distal renal tubular function has not yet been investigated. METHODS: Patients with newly diagnosed type 1 diabetes mellitus were classified into those with DKA and those without DKA, and their proximal and distal renal tubular functions were investigated. The diagnostic criteria for DKA were blood glucose > 200 mg/dL, blood pH < 7.3 or HCO3- < 15 mEq/L, and urine ketone body positivity. RESULTS: Six patients with DKA and five patients without DKA were included. In patients with DKA, urinary β2-microglobulin levels were significantly higher, while blood pH, HCO3-, and tubular reabsorption of phosphorus were significantly lower than in those without DKA. There were no significant differences in blood glucose, HbA1c, serum phosphorus, urinary N-acetyl-beta-glucosaminidase, and urinary amino acid excretion between patients with and without DKA. Elevated NH3 levels and impaired urinary acidification were not observed in patients with and without DKA. CONCLUSIONS: In patients with newly diagnosed type 1 diabetes mellitus complicated with DKA, multiple proximal renal tubular dysfunctions occur simultaneously, suggesting transient Fanconi syndrome. Distal renal tubular acidosis was unlikely. The diagnostic criteria for DKA are appropriate also in the view of proximal renal tubular dysfunction and are considered suggestive of pathophysiological factors that may cause proximal renal tubular dysfunction.

BACKGROUND: The immunosuppressant mizoribine (Miz) can reduce progression of childhood IgA nephropathy (IgAN). This study examined whether Miz affects CD163+ M2-type macrophages which are associated with kidney fibrosis in childhood IgAN. METHODS: A retrospective cohort of 90 children with IgAN were divided into groups treated with prednisolone (PSL) alone (P group; n = 42) or PSL plus Miz (PM group; n = 48) for a 2-year period. Normal human monocyte-derived macrophages were stimulated with dexamethasone (Dex), or Dex plus Miz, and analyzed by DNA microarray. RESULTS: Clinical and histological findings at first biopsy were equivalent between patients entering the P and PM groups. Both treatments improved proteinuria and haematuria, and maintained normal kidney function over the 2-year course. The P group exhibited increased mesangial matrix expansion, increased glomerular segmental or global sclerosis, and increased interstitial fibrosis at 2-year biopsy; however, the PM group showed no progression of kidney fibrosis. These protective effects were associated with reduced numbers of glomerular and interstitial CD163+ macrophages in the PM versus P group. In cultured human macrophages, Dex induced upregulation of cytokines and growth factors, which was prevented by Miz. Miz also inhibited Dex-induced expression of CD300E, an activating receptor which can prevent monocyte apoptosis. CD300e expression by CD163+ macrophages was evident in the P group, which was reduced by Miz treatment. CONCLUSION: Miz halted the progression of kidney fibrosis in PSL-treated pediatric IgAN. This was associated with reduced CD163+ and CD163+CD300e+ macrophage populations, plus in vitro findings that Miz can suppress steroid-induced macrophage expression of pro-fibrotic molecules. A higher resolution version of the Graphical abstract is available as Supplementary information.

Thrombotic microangiopathy (TMA) is a disease that causes organ damage due to microvascular hemolytic anemia, thrombocytopenia, and microvascular platelet thrombosis. Streptococcus pneumoniae-associated TMA (spTMA) is a rare complication of invasive pneumococcal infection. In addition, atypical hemolytic uremic syndrome (aHUS) is TMA associated with congenital or acquired dysregulation of complement activation. We report the case of a nine-month-old boy with refractory nephrotic syndrome complicated by spTMA in the setting of heterozygous complement factor-I (CFI) gene mutation and CFHR3-CFHR1 deletion. He repeatedly developed thrombocytopenia, anemia with schistocytes, hypocomplementemia, and abnormal coagulation triggered by infection, which manifested clinically with convulsions and an intraperitoneal hematoma. Eculizumab (a monoclonal humanized anti-C5 antibody) provided transient symptomatic benefit including improvement in thrombocytopenia; however, he developed unexplained cardiac arrest and was declared brain dead a few days later. In this report, we highlight the diagnostic challenges of this case and the causal relationship between spTMA and complement abnormalities and consider the contribution of heterozygous mutation of CFI and CFHR3-CFHR1 deletion.

Abstract Alport syndrome is a hereditary disorder characterized by renal impairment, hearing loss, and ocular symptoms and is caused by COL4A3, COL4A4, and COL4A5 mutations. Here, we report the case of 3-year-old boy with isolated hematuria detected in routine preventative urinary screening conducted in 3-year-old children. He carried a novel variant, NM_033380.3:c. 1032 + 1 G &gt; A, which caused a splicing abnormality in COL4A5. He was diagnosed with X-linked Alport syndrome.

Maturity-onset diabetes of the young (MODY) is a form of diabetes mellitus characterized by autosomal dominant inheritance, early onset, and the absence of pancreatic autoimmune markers. MODY-causing mutations have been identified in 14 genes, and carboxyl ester lipase (CEL) has been implicated in MODY8. We report a Japanese patient with MODY who harbored a heterogeneous mutation in CEL exon 2 (NM_001807.4:c.146_147delCT; NP_001798.2:p.Ser49CysfsTer52). A 13-year-old girl experienced her first episode of diabetic ketoacidosis, during which her endogenous insulin secretion was poor. However, her insulin secretion had apparently recovered 2 months after the commencement of insulin treatment, and no further treatment was required for the following 2 years. Diabetic ketoacidosis recurred when the patient was 15 years old, when her insulin secretion was again poor. Since that time, the patient, who is now 18 years old, has been undergoing continuous insulin treatment. The large fluctuations in her insulin secretory capacity led us to suspect MODY. MODY8 patients that carry a mutation in the variable number of tandem repeats in the last exon of the CEL gene typically show pancreatic exocrine dysfunction. However, in the present case, which features premature termination, there is no involvement of exocrine dysfunction, potentially demonstrating a genotype-phenotype correlation.

BACKGROUND: Several immunosuppressants have been used to treat children with steroid-dependent nephrotic syndrome (SDNS). Mizoribine (MZR) is an immunosuppressant used to maintain remission in children with SDNS, although its effectiveness for treating SDNS remains controversial. Therefore, in this study, we assessed the clinical factors associated with children having SDNS who were successfully treated with MZR. METHODS: A total of 47 children with SDNS who underwent MZR treatment were retrospectively evaluated. Clinical features including pharmacokinetics after MZR administration were compared between MZR responders and non-responders. RESULTS: The comparison of the two groups revealed no significant differences in age, body weight (BW), daily dose of MZR per BW, serum concentration 2 h after administration (C2), peak serum concentration (Cmax), and area under the concentration curve 0-4 h after administration (AUC0-4). C2/(single dose/BW), Cmax/(single dose/BW), and AUC0-4/(single dose/BW) were significantly higher in the MZR responders than in the non-responders (all p < 0.01). Receiver operating characteristic analysis revealed that the cutoff values of C2 (single dose/kg), Cmax/(single dose/BW), and AUC0-4/(single dose/BW) were 0.55, 0.58, and 1.37, respectively. CONCLUSIONS: MZR is a useful immunosuppressant for treating frequent-relapse NS in children who are susceptible to the drug. The efficacy of MZR may be associated with not only serum concentrations defined by the dosage or absorption efficiency through MZR transporters, but also the susceptibility defined by the expression level and performance of MZR transporters on the target cells.