Clinical utility gene card for: Dent disease (Dent-1 and Dent-2)

Cystinosis induced by CTNS gene mutation: a rare disease study

A boy, aged 1 year and 6 months, was found to have persistent positive urine glucose at the age of 4 months, with polydipsia, polyuria, and growth retardation. Laboratory examinations suggested that the boy had low specific weight urine, anemia, hypokalemia, hyponatremia, hypomagnesemia, metabolic acidosis, glycosuria, acidaminuria, increased fractional excretion of potassium, and decreased tubular reabsorption of phosphate. X-ray examinations of the head, thorax, and right hand showed changes of renal rickets. The slit-lamp examination showed a large number of cystine crystals in the cornea. The genetic testing showed a suspected pathogenic homozygous mutation of the CTNS gene, C.922g>A(p.Gly308Arg). The boy was finally diagnosed with cystinosis. At the beginning of treatment, symptomatic supportive treatment was given to maintain the stability of the internal environment, and cysteamine tartaric acid capsules were used after diagnosis to remove cysteine. This article reported a case of cystinosis caused by CTNS gene mutation and summarized the etiology, clinical features, diagnosis, and treatment of this disease, which can provide a reference for the early diagnosis, treatment, and subsequent study of the disease.

Proteinuria-take a closer look!

Proteinuria is a hallmark of kidney disease. Therefore, measurement of urine protein content plays a central role in any diagnostic work-up for kidney disease. In many cases, proteinuria analysis is restricted to the measurement of total protein content knowing that very high levels of proteinuria (nephrotic proteinuria) are characteristic of glomerular disease. Still, proteinuria can also be a manifestation of impaired tubular protein reabsorption or even be physiological. This review will discuss the physiology of renal protein handling and give guidance on a more sophisticated analysis of proteinuria differentiating albumin, low-molecular weight proteins and immunoglobulins. These non-invasive tests are available in most routine clinical laboratories and may guide the clinician in the diagnostic process before ordering far more expensive (molecular genetic testing) and/or invasive (kidney biopsy) diagnostics.

Nephrolithiasis and Nephrocalcinosis in Childhood-Risk Factor-Related Current and Future Treatment Options

Nephrolithiasis, urolithiasis, and nephrocalcinosis (NC) have become common causes of hospitalization and referral to pediatric outpatient clinics. It is of utmost importance to start with diagnostic evaluation directly after the first passage of a kidney stone, or if NC is diagnosed, in each pediatric patient. This is necessary, as in about 80% of children a metabolic reason for stone disease is detected. Current treatment options are scarce and mainly include general measures like an increased fluid intake or elevating the solubility of a lithogenic substance. According to the given lithogenic risk factor(s), specific treatment options are available and are being summarized in this review. Furthermore, an outlook on potential future treatment options, including innovative strategies such as mRNA-based or recombinant enzyme substitution therapy, is given.

Dent disease in Poland: what we have learned so far?

PURPOSE

Dent disease (DD) is a rare tubulopathy characterized by proximal tubular dysfunction leading to chronic kidney disease (CKD). The aim of the study was to characterize patients with DD in Poland.

METHODS

A retrospective analysis of a national cohort with genetically confirmed diagnosis.

RESULTS

Of 24 males, all patients except one carried mutations in the CLCN5 gene; in one patient a mutation in the OCRL gene was disclosed. Molecular diagnosis was delayed 1 year on average (range 0-21 years). The most common features were tubular proteinuria (100%), hypercalciuria (87%), and nephrocalcinosis (56%). CKD (≤stage II) and growth deficiency were found in 45 and 22% of patients, respectively. Over time, a progression of CKD and persistence of growth impairment was noted. Subnephrotic and nephrotic proteinuria (20%) was found in most patients, but tubular proteinuria was assessed in only 67% of patients. In one family steroid-resistant nephrotic syndrome prompted a genetic testing, and reverse phenotyping. Five children (20%) underwent kidney biopsy, and two of them were treated with immunosuppressants. Hydrochlorothiazide and angiotensin-converting enzyme inhibitors were prescribed for a significant proportion of patients (42 and 37.5%, respectively), while supplemental therapy with phosphate, potassium, vitamin D (12.5% each), and alkali (4.2%) was insufficient, when compared to the percentages of patients requiring repletion.

CONCLUSIONS

We found CLCN5 mutations in the vast majority of Polish patients with DD. Proteinuria was the most constant finding; however, tubular proteins were not assessed commonly, likely leading to delayed molecular diagnosis and misdiagnosis in some patients. More consideration should be given to optimize the therapy.