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University Children’s Hospital Kiel Schwanenweg 20, 24105 Kiel, Germany
Until recently, the familial form of persistent hyperinsulinemic hypoglycemia of infancy (PHHI) was considered to be inherited as an autosomal recessive trait (1). Linkage analysis of this familial form has resulted in the detection of two mutated genes located on chromosome 11p14-15.1. Both of them, SUR1, the gene for a sulfonylurea receptor (2) and Kir6.2 (3) encode subunits of a potassium channel. In the JCEM, Kukuvitis et al. (4) recently reported a French-Canadian kindred, in which PHHI is inherited in an autosomal dominant manner and is linked neither to the SUR1 nor to the Kir6.2 locus. Over three generations, hypoglycemia with severe sequelae or early death was documented. In two of five affected first cousins in generation III, documented hypoglycemia could be associated with hyperinsulinemia. As consanguinity between the parents was ruled out, this pedigree provides evidence for the existence of an autosomal dominant form of PHHI.
Because the authors were not able to demonstrate hyperinsulinism in the generations II and I, we describe a German family with documented hyperinsulinism in two generations. Our index patient is the second child of nonconsanguineous German parents. The girl was born at term with a birth weight of 2800 g. During the newborn period tetralogy of Fallot was diagnosed. At that time no hypoglycemia was noted. At the age of 15 months, the patient had a first hypoglycemic seizure (plasma glucose 36 mg/dL). Since the age of 19 months hypoketotic hypoglycemia was repeatedly documented in the fasted and in the fed state. During hypoglycemic episodes, plasma insulin concentration was repeatedly found to be elevated up to a value of 16.9 µU/mL. Consecutively, the insulin (µU/mL)/glucose (mg/dL) ratio was elevated (0.54, normal <0.4). An oral provocation test with leucine (150 mg/kg) resulted in severe hypoglycemia from inappropriately high insulin secretion (insulin/glucose ratio up to 0.9). Other causes of hypoglycemia were excluded (normal values for plasma cortisol, growth hormone, lactate, ammonia, amino acids, and urine organic acids). On ultrasound no focal lesion in the pancreas was detected.
The child’s mentally retarded mother and her sister are also suffering
from PHHI (see pedigree in Fig. 1
).The mother had her first symptoms when she was 11 months old, the
mother’s sister at the age of 6 months. In both cases hyperinsulinemia
could be documented. During hypoglycemia plasma insulin concentrations
were increased to values of 71 µU/mL and 43 µU/mL, respectively,
resulting in insulin/glucose ratios of 6.5 and 3.9 respectively. Three
other siblings of the mother are not affected. The mother’s mother
also had documented hypoglycemia. Further examinations, however, were
not performed on her. We have no information on our patient’s younger
sister, who was adopted by another family soon after birth.
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Footnotes
Address correspondence to: Markus Hufnagel, M.D., Department of Pediatrics, University Children’s Hospital Kiel, Schwanenweg 20, 24105 Kiel, Germany.
Received March 16, 1998.
References
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