title: Missed congenital hypothyroidism in an identical twin.
abstract: Newborn screening for congenital hypothyroidism has been remarkably effective, although rare cases of false negative screening have been reported in same sex twins, presumptively due to fetal blood exchange. We report a case in which the diagnosis of congenital hypothyroidism due to thyroid ectopia in a monozygotic twin was delayed by 8 months, with a normal newborn screening TSH level of 11 mIU/L blood (normal < 15 mIU/L) at 2 days of life. This is the first such case since the national New Zealand newborn screening programme introduced screening for congenital hypothyroidism in 1981 (30 years ago). Repeating thyroid studies at 14 days of age in same-sex twins has been advocated to avoid delayed diagnosis, but given the low risk, may not be cost effective. It is important to maintain a high index of suspicion in same-sex twin pregnancies of potential congenital hypothyroidism.
authors.affiliation: Starship Children's Hospital, Auckland, New Zealand.
authors.forename: Anita
authors.initials: A
authors.lastname: Azam
authors.forename: Wayne
authors.initials: W
authors.lastname: Cutfield
authors.forename: Fran
authors.initials: F
authors.lastname: Mouat
authors.forename: Paul L
authors.initials: PL
authors.lastname: Hofman
authors.forename: Craig
authors.initials: C
authors.lastname: Jefferies
authors.forename: Dianne
authors.initials: D
authors.lastname: Webster
authors.forename: Alistair Jan
authors.initials: AJ
authors.lastname: Gunn
mesh_terms: D003409:Congenital Hypothyroidism / Q000175:diagnosis*; D057210:Delayed Diagnosis; D004200:Diseases in Twins / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015997:Neonatal Screening; D014430:Twins, Monozygotic