The Health Resources and Services Administration of
the US Department of Health and Human Services and the American College of Medical Genetics both
recommend newborn screening (NBS) for three of the
six urea cycle disorders (UCDs): arginosuccinicaciduria
(ASL), citrullinaemia (ASS), and arginase deficiency
(ARG) (Anonymous 2006). Newborn screening for
these disorders facilitates early diagnosis, is likely to
improve outcomes, and makes the most efficient use of
the health care team. Early detection of these three
disorders may allow for the judicious use of nitrogenscavenging
drugs, together with adequate and rapid
nutritional intervention, with the aim of improving the
outcome.
Even with the use of NBS, not all UCDs are
detected during the newborn period. In clinical practice,
patients can be categorized into early-onset or
late-onset. The early-onset or neonatal group tends to
have more severe forms of the disorders than the lateonset
group, who present after the neonatal period
(Brusilow and Horwich 2001). Patients from the latter
group have presented to clinic at ages ranging from
infancy to 60 years with symptoms from minor
behavioural changes to coma.