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Symptomatic west syndrome in neonatal diabetes and developmental delay (DEND-syndrome)?
Neonatal diabetes is a condition with an incidence of 1:500.000 newborns. Heterozygous activating mutations in KCNJ11, which encodes the Kir 6.2 subunit of the pancreatic ATP-sensitive potassium channel and hence inhibits insulin secretion, cause 35–60% of permanent neonatal diabetes. In about 10% of these patients additional neurological abnormalities like muscle weakness, disturbances of speech and epilepsy occur. As a new entity DEND-syndrome (developmental delay-epilepsy-neonatal diabetes) has been described, in which generalized epilepsy is most common and hypsarrhythmia has been observed in some cases.
We present a 16 months old girl with manifestation of diabetes at the age of 6 months and continuous subcutaneous insulin therapy. At admission to hospital she already showed a marked developmental delay, during the first weeks after diagnosis of diabetes she developed infantile spasms and a beginning hypsarrhythmia in the eeg. In the genetic investigation a new mutation in KCNJ11 (c.152 A>C) was found. After a basic metabolic work up and a normal MRI scan of the brain we started an anticonvulsive treatment with sultiam at the same time as a therapy with sulfonylurea. After 3 days seizures had ceased, the eeg showed only single epileptic discharges. Furtheron, the patient had HbA1c values around 6.5% without insulin and showed progress in the psychomotoric development. Meanwhile the anticonvulsive treatment has been tapered without recurrence of seizures.
The above case demonstrates that in DEND-syndrome under a therapy with sulfonylurea the neurological deficits can improve markedly. It remains unclear so far, if the mutation that is responsible for the decreased insulin secretion also influences CNS-specific potassium channels and hence causes the infantile spasms.