The Term Newborn: Hypoglycemia.

This review provides an update on neonatal hypoglycemia in the term infant, including discussion of glucose metabolism, definitions of hypoglycemia, identification of infants commonly at risk, and the screening, treatment, and potential neurologic outcomes of postnatal hypoglycemia. Neonatal hypoglycemia is a common metabolic condition that continues to plague clinicians because there is no clear relationship between low glucose concentrations or their duration that determines adverse neurologic outcomes. However, severely low, prolonged, recurrent low glucose concentrations in infants who also have marked symptoms such as seizures, flaccid hypotonia with apnea, and coma clearly are associated with permanent brain damage. Early identification of at-risk infants, early and continued breastfeeding augmented with oral dextrose gel, monitoring prefeed glucose concentrations, treating symptomatic infants who have very low and recurrent low glucose concentrations, and identifying and aggressively managing infants with persistent hyperinsulinemia and metabolic defects may help prevent neuronal injury.

ABO maternal-child discordance: Evidence of variable allelic expression and considerations for investigation.

BACKGROUND: We report a case of apparent mother-child ABO group noninheritance. A Caucasian mother initially typed as group O and her infant group AB. Investigation ruled out preanalytical causes such as mislabeled samples and in vitro fertilization. MATERIALS AND METHODS: Red blood cells were characterized by routine serologic testing. Genomic data were analyzed by targeted polymerase chain reaction-restriction fragment length polymorphism and Sanger sequencing. Transferase structures were modeled using PyMOL molecular visualization software. RESULTS: Serologic testing initially demonstrated the mother was group O, father group AB, and infant group AB. Further testing of the maternal sample with anti-A,B demonstrated weak A expression. Molecular testing revealed the maternal sample had an ABO*O.01.01 allele in trans to an A allele, ABO*AW.29 (c.311T>A, p.Ile104Asn), determined by gene sequencing. The sample from the infant carried the same ABO*AW.29 allele in trans to a B allele, ABO*B.01. CONCLUSION: ABO genotyping revealed an A transferase encoded by ABO*AW.29, with apparent variable activity. Although A antigen expression is well known to be weak in newborns, it was robust on the red blood cells (RBCs) of the AB infant and undetectable with anti-A on the mother. Variable expression of weak subgroups may reflect competition or enhancement by a codominant allele, as well as glycan chain maturation on red cells. Previous examples in group AB mothers with Aweak infants suggested that the decreased expression is primarily due to glycan immaturity. To our knowledge, this is the first reported case of the ABO*AW.29 allele presenting with weak A expression in a group Aweak mother and robust A expression in a group AB infant, suggesting the in trans allele is an important factor in determining transferase activity and may override age-related effects.