Neonatal diabetes has been shown to be associated with high neuropsychiatric morbidity in a genotype-phenotype–dependent manner. However, the specific impact of different mutations on intellectual functioning is still insufficiently characterized. Specifically, only a small number of subjects with developmental delay have been comprehensively assessed, creating a knowledge gap about patients carrying the heaviest burden.
We assessed the intellectual functioning and mental health of the complete Norwegian population with KATP channel neonatal diabetes. Eight sulfonylurea-treated children (five with the p.V59M genotype [KCNJ11]) were assessed using age-matched control subjects with type 1 diabetes. The investigations included a physical and motor developmental examination, cerebral MRI, psychometrical examination, and questionnaires assessing intellectual capabilities and psychiatric morbidity.
A strong genotype-phenotype correlation was found, revealing the p.V59M genotype as highly associated with substantial intellectual disability, with no significant correlation with the time of sulfonylurea initiation. Consistent with previous studies, other genotypes were associated with minor cognitive impairment. Cerebral MRI verified normal brain anatomy in all but one child.
We here presented a comprehensive assessment of intellectual functioning in the largest cohort of p.V59M subjects to date. The level of intellectual disability revealed not only changes the interpretation of other psychological measures but downplays a strong protective effect of sulfonylurea. Within the scope of this study, we could not find evidence supporting an early treatment start to be beneficial, although a weaker effect cannot be ruled out.