The Turkish Journal of Pediatrics 2012 , Vol 54 , Num 2
Hypomagnesemia-Hypercalciuria-Nephrocalcinosis and Ocular Findings: A New Claudin-19 Mutation
1Division of Pediatric Nephrology, Department of Pediatrics, and 2Department of Ophthalmology, Kocaeli University Faculty of Medicine, Kocaeli, Turkey, and 3Department of General Pediatrics, Pediatric Nephrology, University Children’s Hospital, Münster, Germany Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is an autosomal recessive syndrome that affects the tight junction proteins claudin-16 and claudin-19 in the thick ascending limb. In patients with claudin-19 mutations, additional symptoms such as visual impairment and other ophthalmologic findings are expected.

In this report, we present a seven-year-old girl with polyuria and polydipsia. She was the daughter of consanguineous parents with a history of neonatal hypomagnesemic convulsion. On physical examination, bilateral horizontal nystagmus, retinitis pigmentosa and severe myopia were detected. Laboratory examination revealed hypomagnesemia, hypercalciuria and hypermagnesuria. A clinical diagnosis of FHHNC caused possibly by claudin-19 mutation was decided with the ocular findings. DNA analysis revealed a novel homozygous nonsense mutation (W169X) in the CLDN19 gene.

In conclusion, in a patient with consanguineous parents, history of hypomagnesemic convulsion and disturbed organization and development of the retina, a diagnosis of FHHNC caused by claudin-19 mutation should be considered. Keywords : hypomagnesemia, hypercalciuria, nephrocalcinosis, retinitis pigmentosa, nystagmus, myopia, claudin-16, claudin-19.

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