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Abstract
Objectives: Activating mutations in the human KCNJ11 gene, encoding the pore-forming subunit (Kir6.2) of the ATP-sensitive potassium (KATP) channel, are one cause of neonatal diabetes mellitus. In a few patients, KCNJ11 mutations cause a triad of developmental delay, epilepsy, and neonatal diabetes (DEND syndrome). The aim of this study was to determine the clinical effects, functional cause, and sensitivity to sulfonylurea treatment of a novel KCNJ11 mutation producing DEND syndrome.
Methods: We screened the DNA of a 3-year-old patient with neonatal diabetes, severe developmental delay, and therapy-resistant epilepsy for mutations in KCNJ11. We carried out electrophysiologic analysis of wild-type and mutant KATP channels heterologously expressed in Xenopus oocytes.
Results: We identified a novel Kir6.2 mutation (I167L) causing DEND syndrome. Functional analysis showed both homomeric and heterozygous mutant channels were less inhibited by MgATP leading to an increase in whole-cell KATP currents. This effect was due to an increase in the intrinsic open probability. Heterozygous channels were strongly inhibited by the sulfonylurea tolbutamide. Treatment of the patient with the sulfonylurea glibenclamide not only enabled insulin therapy to be stopped, but also resulted in improvement in epilepsy and psychomotor abilities.
Conclusions: We report a case of developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome that shows neurologic improvement with sulfonylurea therapy. Early recognition of patients with DEND syndrome may have considerable therapeutic benefit for the patient.
Footnotes
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Editorial, see page 1310
e-Pub ahead of print on July 25, 2007, at www.neurology.org.
*Both authors contributed equally to this publication.
Supported by the Wellcome Trust, the Royal Society, the European Union (Integrated Project EuroDia LSHM-CT-2006-518153 in the Framework Programme 6 [FP6] of the European-Community), and the Research & Development Directorate at the Royal Devon & Exeter NHS Foundation Trust. F.M.A. is a Royal Society Research Professor.
Disclosure: The authors report no conflicts of interest.
Received February 21, 2007. Accepted in final form April 17, 2007.
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