Familial persistent hyperinsulinemic hypoglycemia of infancy (PHHI), an autosomal recessive disorder characterized by unregulated insulin secretion, is linked to chromosome 11p14-15.1. The newly cloned high-affinity sulfonylurea receptor (SUR) gene, a regulator of insulin secretion, was mapped to 11p15.1 by means of fluorescence in situ hybridization. Two separate SUR gene splice site mutations, which segregated with disease phenotype, were identified in affected individuals from nine different families. Both mutations resulted in aberrant processing of the RNA sequence and disruption of the putative second nucleotide binding domain of the SUR protein. Abnormal insulin secretion in PHHI appears to be caused by mutations in the SUR gene.
Autosomal recessive pseudohypoaldosteronism type I is a rare life-threatening disease characterized by severe neonatal salt wasting, hyperkalaemia, metabolic acidosis, and unresponsiveness to mineralocorticoid hormones. Investigation of affected offspring of consanguineous union reveals mutations in either the alpha or beta subunits of the amiloride-sensitive epithelial sodium channel in five kindreds. These mutations are homozygous in affected subjects, co-segregate with the disease, and introduce frameshift, premature termination or missense mutations that result in loss of channel activity. These findings demonstrate the molecular basis and explain the pathophysiology of this disease.
Over a 3-year period, the diagnosis of persistent neonatal hyperinsulinism (PNH) was made in seven infants, from an unselected cohort of 18,726 births, all of Saudi Arabian origin. Thus the incidence of PNH was one in 2,675 births. The high incidence, associated consanguinity, and occurrence in siblings suggest that PNH may be inherited as an autosomal recessive disorder.
Growth failure associated with severe primary insulin-like growth factor 1 (IGF-1) deficiency (SPIGFD), a condition defined as basal IGF-1 standard deviation score (SDS) less than or equal to −3 and height SDS less than or equal to −3 in a child with normal or elevated levels of growth hormone, can be successfully treated with the recombinant human IGF-1 mecasermin. In this review, we describe the most safe and effective way to use mecasermin in the treatment of patients with SPIGFD, including how to initiate dosing, key side effects, and how to monitor treatment. Finally, mention of how to reinitiate therapy is made, given the recent drug shortage with mecasermin.
SUMMARY Seven infants with persistent neonatal hyperinsulinism were treated in Dhahran Health Centre from 1983 to 1986. The insulin:glucose ratio (serum insulin concentration pmolIl) divided by the blood glucose concentration (mmolI1) ranged from 12 to 636, mean (SD) 177 (201). To control hypoglycaemia, diazoxide (12-24 mg/kg/day) was given in a continuous intravenous glucose infusion (12-22 mg/kg/min) on 11 separate occasions, four infants twice each and three infants once each. An increase of more than one standard deviation in the heart and respiratory rates, together with other symptoms of heart failure, was considered to be evidence of diazoxide toxicity. Cardiorespiratory failure (toxicity) occurred on eight of the 11 occasions (73%) in seven infants. The average daily fluid intake, weight change, respiratory rate and heart rate before treatment were similar whether or not the infant developed toxicity. A diazoxide toxicity index was obtained by multiplying the dose of diazoxide by the insulin:glucose ratio to relate the diazoxide dose to the severity of the disease. In all instances when the toxicity index was more than 1533 (mean (SD) 3732 (2741)) cardiac toxicity developed. In contrast, infants with a toxicity index of less than 675 (mean (SD) 364 (270)
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