A neonate is born at 38 weeks gestation age via spontaneous vaginal delivery to a 40-year-old woman. The mother was working in South America when she discovered that she was pregnant. She had 2 days of fever associated with cough and swollen cervical glands, which resolved spontaneously at 12 weeks gestation prior to returning to the United States. The mother has no current symptoms. Neonatal examination shows weight and length at the 8th percentile, and head circumference below the 3rd percentile for age. Heart and lung sounds are normal. There is moderate hepatosplenomegaly. Skin examination shows diffuse, dark-blue papules and nodules. Serology from the mother and infant are attained. Which of the following serology patterns is most consistent with a suspected congenital infection?

Question

Quizplus · Accepted Answer

11ec160b_37d6_adf6_9249_cbecfde97ee8_MD0001_00 Growth restriction, microcephaly, hepatosplenomegaly, and a diffuse dark-blue rash (ie, blueberry muffin rash) are nonspecific features shared by multiple congenital (TORCH) infections (eg, cytomegalovirus, toxoplasmosis, rubella). These infections are transmitted transplacentally to the fetus from a mother infected during pregnancy. Although maternal symptoms may be mild (eg, fever, lymphadenopathy), the developing fetus can have significant morbidity, particularly with a first trimester infection. Serology and polymerase chain reaction testing can help to determine the diagnosis in a neonate with suspected intrauterine infection. Neonatal antibody titers can be difficult to interpret, particularly due to maternal transfer of some antibodies and not others: Maternal IgM does not cross the placenta, so detection of organism-specific IgM in a symptomatic neonate is diagnostic. At birth, virtually all infant IgG is maternally derived IgG that crossed the placenta, and elevated maternal IgG would be expected in this mother with infectious symptoms 6-7 months prior to delivery (Choices A and D). Therefore, organism-specific newborn IgG (eg, Toxoplasma IgG) will also be elevated in the setting of a past maternal infection. (Choice C) Maternal IgM may be negative with a remote infection (as with this mother) or positive if recently infected. False negative IgM titers can also occur in neonates with congenital infection whose IgM waned before birth or in those who have yet to form a robust immune response. However, a positive newborn IgG would be expected due to transplacental transfer of maternal IgG. Educational objective: Organism-specific IgM is diagnostic of congenital infection in a symptomatic neonate (eg, growth restriction, microcephaly, hepatosplenomegaly, blueberry muffin rash). Because maternal IgG titers are expected with a past infection and neonatal IgG at birth is maternally derived, elevated newborn IgG is also expected. __________ References: Laboratory diagnosis of congenital toxoplasmosis. (http://www.ncbi.nlm.nih.gov/pubmed/27147724)

A Neonate Is Born at 38 Weeks Gestation Age Via