Infantile Nephropathic Cystinosis Presenting as Bartter-like Syndrome in Infancy: A Case Report with CTNS Gene Variant
TL;DR
This case highlights that infantile nephropathic cystinosis should be considered in infants presenting with hypokalaemia, persistent polyuria, polydipsia, failure to thrive, and elevated plasma renin, even in the absence of classical Fanconi syndrome or corneal cystine crystals.
Abstract
Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene, leading to cystine accumulation and multiorgan involvement. It typically presents with features of proximal tubular dysfunction; however, atypical presentations may pose diagnostic challenges. In the present case, a male infant, aged 11 months, who was born out of a non-consanguineous marriage was brought to the hospital with a history of failure to thrive, polyuria, and polydipsia. Both his height and weight were below the third percentile. Bartter syndrome like tubulopathy was suggested by hypokalaemia, and elevated renin levels. Following initiation of Indomethacin therapy for suspected Bartter’s syndrome, there was partial clinical improvement in symptoms. The results of the ocular examination were normal. Whole exome sequencing identified a mutation in the CTNS that causes infantile nephropathic cystinosis. This case highlights that infantile nephropathic cystinosis should be considered in infants presenting with hypokalaemia, persistent polyuria, polydipsia, failure to thrive, and elevated plasma renin, even in the absence of classical Fanconi syndrome or corneal cystine crystals.