A number of congenital disorders characterized by low blood sugar levels (hypoglycemia) as a result of excessive secretion of the hormone insulin are collectively known as congenital hyperinsulinism.
These disorders are caused by genetic mutations that result in mutant KATP channel proteins in the insulin-secreting cells of the pancreas. To develop the most common and most severe form of congenital hyperinsulinism a baby must inherit a mutated gene from each of its parents (these mutations are said to be recessive as if only one mutated gene is inherited the baby does not suffer from the disease).
Recent reports have suggested that less severe forms of the disease can arise in children through the inheritance of a mutated gene from only one parent (these mutations are said to be dominant as the mutated gene causes disease despite the presence of a normal version of the gene).
To better understand the differences between the recessive and dominant mutations that cause congenital hyperinsulinism, Charles Stanley and colleagues, at the Children's Hospital of Philadelphia, characterized 33 patients with dominantly inherited KATP mutations.
Consistent with the recent reports on a small number of children, the authors found that patients with disease caused by dominant mutations exhibited a milder hypoglycemia than is normal for individuals with congenital hyperinsulinism caused by recessive mutations. Indeed, there were a large number of asymptomatic individuals and disease in most symptomatic individuals was well controlled with medication.
Mechanistic insight into the difference in the severity of disease caused by dominant and recessive mutations was provided by the observation that dominant mutations generated a form of KATP that can reach the cell surface but has impaired activity, whereas recessive mutations are known to generate a form of KATP that cannot reach the cell surface.
The authors stress that because children with dominant KATP mutations are likely to exhibit less severe symptoms, the disease may be missed and doctors should carefully evaluate children with family histories of the disease.
- Sara E. Pinney et al. Clinical characteristics and biochemical mechanisms of congenital hyperinsulinism associated with dominant KATP channel mutations. Journal of Clinical Investigation, July 1, 2008
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