Acute calcium, phosphorus, or magnesium metabolic disturbances are rare. However, without accurate knowledge, clinicians cannot provide appropriate treatment. I aimed to perform a review to summarize the differences in symptoms depending on the severity of electrolyte imbalances, the causes, timing of clinically necessary interventions even in asymptomatic patients, and precautions to be observed when administering injectable drugs. Due to the increase in therapeutic drugs for various diseases and the elucidation of novel associated pathologies, the chances of encountering electrolyte disorders are increasing. Thus, knowledge of the electrolyte imbalances, appropriate collection of urine and blood samples for accurate diagnosis, and treatment are important for all clinicians.

Background: The optimal treatment for C3 glomerulopathy remains undefined. Methods: 10 cases of C3 glomerulopathy diagnosed at our hospital between January 1, 2011 and September 30, 2021 were included in this study. We evaluated the proportion of C3 glomerulopathy, clinical course, treatment, and efficacy. Results: 10 cases of C3 glomerulopathy were included. 9 of the 10 patients were initially treated with steroid pulse and Mizoribine (“MZR”) and 1 with predonisolon alone. The median urine protein creatinine ratio (UP/C) on admission was 1.34 g/g・Cre. At 1 month after initial treatment, the median UP/C decreased to 0.42 g/g・Cre, and all patients improved; 6 patients were subsequently added or changed from MZR to cyclosporine (“CyA”), and the median UP/C reduced from 0.92 g/g・Cre to 0.13 g/g・Cre in 4 patients after more than six months post initiation of CyA. Conclusion: Multidrug therapy, including steroids and MZR as initial treatment, was successful. If initial treatment was inadequate or ineffective, CyA was considered as an effective option.

As most children with stage 3–5 chronic kidney disease (CKD) in Japan present with nonglomerular disease, its detection is difficult during annual urinalysis conducted in school. Since 2020, in Uwajma city, Japan, to screen pediatric CKD, the practice of measuring serum creatinine (Cr) levels was introduced in addition to the pediatric lifestyle-related disease checkup, which involved measuring total and HDL cholesterol levels in fourth-grade elementary school children. Decisions regarding positive screening were made according to the Cr-based estimated glomerular filtration rate (Cr-eGFR). Similar screening practice was initiated in Ozu City in 2022 for fourth graders in elementary school (E4) and first graders in junior high school (J1). Till date, 1,900 E4 and 352 J1 have been screened. The criterion for positive screening was Cr-eGFR level of <90 and 85 mL/min/1.73 m² for E4 and J1, respectively. Accordingly, 125 E4 and 19 J1 were selected for further examination, of which 85 E4 and 11 J1 visited our department. We detected five children with stage 2 or higher CKD and one child with stage 3 CKD in association with autosomal recessive polycystic kidney disease who had never shown abnormal findings upon urine analysis in the school. These findings demonstrate the potential prevalence of CKD in the general pediatric population and the clinical implication of measuring creatinine in pediatric lifestyle-related disease checkups.

We report a case of 14-year-old boy diagnosed with renal sarcoidosis. The patient was brought to our hospital with fever, but physical examination and the laboratory data did not lead to diagnosis. He was evaluated by contrast-enhanced computed tomography (CT) and CT found multiple low dense areas enhanced less than the adjacent normal renal parenchyma, suggesting interstitial nephritis. As further examination, he was underwent Ga-67 scintigrams, which indicated bilateral renal accumulation. Although the renal function was normal at initiation, serum creatinine level increased progressively (1.65 mg/dL) during follow-up and he was underwent renal biopsy to obtain definitive diagnosis. After ruling out other diseases that develop interstitial nephritis, the diagnosis of sarcoidosis was established on histopathology of granulomatous interstitial nephritis from renal biopsy. The renal function improved shortly after corticosteroid therapy and mycophenolate mofetil were introduced. Treatment is necessary in cases with renal insufficiency, and it should be performed before the interstitial fibrosis progresses into renal failure. In addition, the use of MMF conjunction with corticosteroids might have a steroid-sparing role.

Steroid treatment introduced for pediatric nephrotic syndrome has multiple side effects, one of which is glaucoma. Although steroid glaucoma is often improved only by eye drops, there are a few cases that require glaucoma surgery. We experienced a case with severely increased intraocular pressure found precociously after start of steroid treatment at the onset of nephrotic syndrome. Although severe steroid glaucoma was successfully treated by trabeculotomy in both eyes, increased intraocular pressure recurred after steroid treatment for the relapse of nephrotic syndrome. This case carried angle dysgenesis, generally shown in pediatric glaucoma, in addition to the general steroid responder component. Therefore, this case might have a rapid increase in intraocular pressure after steroid treatment, in which glaucoma surgery was urgently required. Because steroid glaucoma can follow rapid and severe course as our case, intraocular pressure should be checked and controlled immediately as possible.

Alport syndrome is a hereditary disease caused by abnormalities in type IV collagen. It is associated with progressive renal failure, hearing loss, and ocular abnormalities. Here, we report the case of a boy with X-linked Alport syndrome whose mother was suspected to have a germline mosaic mutation. A 2-year-old boy presented with persistent hematuria and proteinuria after gross hematuria. The results of renal biopsy showed, only minor changes under light microscopy, all fluorescence antibody tests were negative, and type IV collagen staining was negative for the α5 chain in both the glomerular basement membrane and Bowman’s capsule. Genetic analysis was requested, and a hemizygous mutation was identified in exon 49 of COL4A5, which was thought to be the etiology. Our patient was initially suspected of having de novo mutational X-linked Alport syndrome. However, the patient’s mother had persistent hematuria, and genetic analysis revealed a very small wave of single-nucleotide deletions, suggesting the possibility of germline mosaicism. In this case, more careful genetic counseling is recommended, including the possibility of passing it on to siblings. For a definitive diagnosis, it is important and practical to consider regular urinalysis screening of siblings and genetic analysis of the patient’s mother’s urinary cytoplasm.

The case described here is a six-year-old girl presenting with fever and abdominal pain without any history of urinary tract infection. On interviewing the patient, it emerged that she had developed several problems with micturition after being reprimanded by her father for failing to urinate in the toilet. A urine culture test performed at the time of admission revealed only a small amount of bacteria. Nonetheless, a urinary tract infection was suspected based on the clinical interview. Accordingly, contrast-enhanced CT was performed, revealing acute focal bacterial nephritis and a renal abscess. There were no apparent neurological abnormalities in MRI of the spine, suggesting that the underlying disease may have been Hinman-Allen syndrome. Oral treatment was considered, but the patient’s urinary habits improved solely with appropriate training, and no recurrence of urinary tract infection has been observed to date. This is a rare case of a renal abscess developing without an underlying organic disease, and emphasizes the necessity of interviewing school-age children regarding their micturition habits when they first develop any signs of urinary tract infection. Currently, there are only a few detailed reports on urination training. Because this syndrome may be cured with lifestyle guidance alone, without recurrence in this patient, here we report on the details of the actual training procedure.

Exercise therapy for pediatric patients with active IgA nephropathy is necessary to improve physical mobility functioning and maintaining a normal daily and school-life, whilst managing the risk of further relapse; although, this has not been investigated yet. This case report aimed to evaluate the influence of exercise therapy in a pediatric patient with active IgA nephropathy whilst being treated in-hospital with a multiple-drug combination therapy. The patient was an 18-year-old girl diagnosed with IgA nephropathy a year prior to her admission at the hospital for multiple-drug combination therapy. Moderate-intensity exercise therapy was started on the 8th day and continued until the 31st day, at discharge. The results of her physical functioning on the 8th and 30th day were grip strength from 21.1 kg to 21.0 kg, knee extension strength from 0.59 kgf/kg to 0.74 kgf/kg, skeletal muscle mass index from 7.2 kg/m² to 6.7 kg/m², 6-minute walk test from 570 m to 590 m, and peak work rate from 100 watts to 110 watts. Muscle strength and exercise tolerance were maintained, or improved. The urine protein/creatinine ratio (UP/Cr) from the 8th day to discharge decreased from 0.4 g/gCr to 0.2 g/gCr. There was no recurrence of IgA nephropathy during hospitalization. Exercise therapy during hospitalization in a pediatric patient with active IgA nephropathy may not have adverse effects, and may prevent a decline in physical function and exercise tolerance.

This study reports a case of a 14-year-old female who had severe interstitial nephritis associated with primary Sjögren’s syndrome and complicated by abnormal glucose tolerance. At initial examination, her HbA1c level was 6.4% and HOMA-IR was 3.4, indicating increased insulin resistance (IR). Although standard steroid treatment was selected for the underlying disease, there were concerns about exacerbating her abnormal glucose tolerance. However, her abnormal glucose tolerance improved rapidly along with her underlying condition through immunosuppressive therapy, which included steroid pulse therapy. Decreased insulin receptor expression in the renal tubules and increased IR accompanying chronic inflammation are probably involved in the disease progression associated with chronic kidney disease and interstitial nephritis. In cases, such as that of our patient, wherein abnormal glucose tolerance complicates kidney disease, improvement in this tolerance can be expected by treating the underlying condition.

Among cases of polycystic kidney disease (PKD) complicated with tuberous sclerosis (TSC) (TSC-PKD), there have been advancements in gene analysis for TSC2/ PKD1 contiguous gene syndrome with poor renal prognosis. However, there are many unclear points about cases of TSC-PKD without PKD gene abnormalities. We here report a case of a 13-year-old girl who was found to have bilateral PKD while screening for TSC complications. Since TSC2/ PKD1 contiguous gene syndrome was suspected, genetic testing was performed. However, there were no abnormalities in the TSC2 gene, PKD1 gene or even in the PKD2 gene, despite the presence of TSC-PKD with prominent cysts. This result suggests that factors other than abnormalities in the PKD1 and PKD2 genes may be involved in the onset of PKD. Accumulation and analysis of TSC-PKD cases without PKD gene abnormalities are necessary for further elucidation of the pathophysiology of TSC-PKD.

Valacyclovir (VACV) is an acyclovir (ACV) prodrug. We here report a case of a healthy girl who developed acute kidney injury (AKI) after taking a regular dose of VACV. A 14-year-old girl, diagnosed with herpes zoster, was prescribed 3,000 mg/day of VACV by her previous doctor. She then complained of headache, neck and back pain, and generalized edema that appeared on the seventh day. After discontinuing the medication, she was admitted to a hospital, where a blood examination indicated an occurrence of renal functional impairment. AKI caused by VACV was suspected, and hemodialysis was performed 5 and 7 days after admission. A renal biopsy performed 10 days after admission revealed extensive vacuolar degeneration and loss of tubular epithelial cells without interstitial mononuclear cell infiltration or crystal formation, suggesting acute tubular necrosis caused by drug-induced toxic injury. Thereafter, the renal function improved, and she was discharged after 21 days of hospitalization. We later requested measurement of ACV blood concentration in a serum sample taken on day 7, which showed an abnormally high ACV level of 10.69 µg/mL (appropriate concentration: 0.8–1.6 µg/mL). This case indicates that VACV may induce kidney injury even with its regular doses in children with normal renal function. It is necessary to provide appropriate guidance regarding side effects and drinking volume when prescribing VACV to patients and to strive for prevention and early detection.

Numerous drugs have been reported as causes of drug-induced acute tubulointerstitial nephritis (ATIN); however, cases due to fosfomycin have rarely been documented. We herein report a case involving a 3-year-old boy with no medical history who presented with acute renal injury characterized by fosfomycin-induced ATIN. The patient had been treated with fosfomycin for gastroenteritis and developed a rash 24 hours after beginning therapy. Even after fosfomycin was switched to tosufloxacin, he was brought to our hospital because of frequent vomiting and worsening malaise. Although intravenous rehydration therapy was performed, his urine output did not improve, and his blood test showed an elevated serum creatinine concentration. He was admitted to our hospital for treatment of acute kidney injury and underwent renal biopsy on day 5, which showed features of ATIN. A drug-induced lymphocyte transformation test was positive for both fosfomycin and tosufloxacin 8 weeks from symptom onset; 1 year later, however, the test was positive only for fosfomycin. ATIN caused by fosfomycin is very rare. The findings in the present case may indicate the usefulness of a second lymphocyte transformation test when the first test shows positivity for multiple drugs.