Hypophosphatemic rickets due to Dent's disease: A case report and review of literature

Dent disease presenting with nyctalopia and electroretinographic correlates of vitamin A deficiency

Purpose

To report a unique case of Dent Disease presenting with nyctalopia associated with vitamin A deficiency and abnormal electroretinogram findings without prior systemic symptomatology.

Observations

A 16-year-old male presented with a several month history of nyctalopia and peripheral vision deficits. Central visual acuity, anterior and posterior segment examinations, and macular optical coherence tomography were unremarkable. Electroretinogram (ERG) testing revealed a rod-cone dystrophic pattern, with further workup demonstrating serum vitamin A deficiency (VAD). Laboratory evaluation revealed renal dysfunction and proteinuria with a significantly elevated urinary retinol-binding protein (RBP). Kidney biopsy showed glomerular and tubular disease.Genetic screening for inherited renal disease was performed identifying a hemizygous pathogenic variant c.2152C>T (p.Arg718*) in the Chloride Voltage-Gated Channel 5 (CLCN5) gene, confirming the diagnosis of X-linked Dent Disease. Following vitamin A supplementation, our patient reported resolution of nyctalopia and reversal of abnormal ERG findings were demonstrated.

Conclusions and Importance

To our knowledge, this is the first case in the literature describing Dent disease solely presenting with ophthalmic symptoms of nyctalopia and abnormal electroretinogram findings that later reversed with vitamin A repletion. This case stresses the importance for clinicians to consider renal tubular disorders in the differential for VAD.

Phenotype of Dent Disease in a Cohort of Indian Children

OBJECTIVE

To describe the clinical and genotypic features of Dent disease in children diagnosed at our center over a period of 10 years.

DESIGN

Case series.

SETTING

Pediatric Nephrology Clinic at a referral center in Northern India.

METHODS

The medical records of patients with Dent disease diagnosed and followed up at this hospital from June 2005 to April 2015 were reviewed. The diagnosis of Dent disease was based on presence of all three of the following: (i) low molecular weight proteinuria, (ii) hypercalciuria and (iii) one of the following: nephrolithiasis, hematuria, hypophosphatemia or renal insufficiency, with or without mutation in CLCN5 or OCRL1 genes.

RESULTS

The phenotype in 18 patients diagnosed with Dent disease during this period was characterized by early age at onset (median 1.8 y), and polyuria, polydipsia, salt craving, hypophosphatemic rickets and night blindness. Rickets was associated with severe deformities, fractures or loss of ambulation in six patients. Nephrocalcinosis was present in three patients, while none had nephrolithiasis. Generalized aminoaciduria was seen in 13 patients, two had glucosuria alone, and one had features of Fanconi syndrome. Over a median follow up of 2.7 years, one patient developed renal failure. Genetic testing (n=15) revealed 5 missense mutations and 3 nonsense mutations in CLCN5 in 13 patients. Five of these variations (p.Met504Lys, p.Trp58Cys, p.Leu729X, p.Glu527Gln and p.Gly57Arg) have not been reported outside the Indian subcontinent.

CONCLUSION

Our findings suggest a severe phenotype in a cohort of Indian patients with Dent disease.

Effect of growth hormone replacement therapy in a boy with Dent's disease: a case report

INTRODUCTION

Dent's disease is an X-linked recessive proximal tubulopathy characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis, nephrolithiasis and progressive renal failure. To the best of our knowledge, this is only the third report on the use of growth hormone therapy in a child with poor growth associated with Dent's disease.

CASE PRESENTATION

We report on a 7-year-old Montenegrin boy with proteinuria, hypercalciuria, nephrocalcinosis, rickets and short stature with unimpaired growth hormone secretion. A molecular genetic analysis showed S244L substitution on the CLCN5 gene. After two years of conventional treatment with hydrochlorothiazide, laboratory tests revealed more prominent proteinuria, mild hypophosphatemia, increased values of alkaline phosphatase and features of rickets. Phosphate salts, calcitriol, potassium citrate and growth hormone were included in the therapy. After three years of therapy, his adjusted parental stature was 1.53 standard deviations higher than at the initiation of growth hormone therapy. His global kidney functions and levels of proteinuria and calciuria remained relatively stable. In spite of the growth hormone therapy, his tubular reabsorption of phosphate deteriorated.

CONCLUSION

Treatment with recombinant human growth hormone may have a positive effect on final height in poorly growing children with Dent's disease and hypophosphatemic rickets. However, it is not possible to reach definite conclusions due to the small sample within the literature and the brief duration of the therapy.