Not So Rare: Errors of Metabolism During the Neonatal Period

Sandra A. Banta-Wright, MN, RNC, NNP; Robert D. Steiner, MD

Disclosures

NAINR. 2003;3(4) 

In This Article

Abstract and Introduction

During the neonatal period, the diagnosis of an error of metabolism (EM) was once thought to portend a poor prognosis or lethality. Over the past two decades, the prognosis of many EMs has changed. The critical aspect of the metabolic evaluation in a sick newborn is to rapidly identify whether there may be a metabolic problem. If there is a metabolic problem, the goal is to minimize the sequelae of the specific disorder. This review will explore how to approach and evaluate a newborn suspected of having an EM. A discussion of clinical and laboratory findings that often accompany EM will be included.

At delivery, a full-term newborn may appear active and healthy. However, over a course of hours, days, or weeks, nonspecific signs and symptoms of distress may develop. In some cases, there will be a gradual decline in the infant's condition with slow deterioration. Alternatively, the onset of distress can be sudden, catastrophic, and life threatening. The symptoms usually indicate a differential diagnosis of respiratory, cardiac, gastrointestinal, neurological, and infectious disease. There is a tendency to not include consideration of an error of metabolism (EM), formerly referred to as an inborn error of metabolism, until the above "more common causes of distress" have been excluded–this approach can be fatal. During the first year of life, EMs mimic or even predispose to these conditions. Individual EMs are, for the most part, indeed rare. Collectively, however, EM disorders are not an infrequent cause of distress in the neonatal period. It is now estimated that 1 in 1,000 newborns is at risk for being affected by an EM.[1] Due to the large numbers of EM that can present during the neonatal period, some fear that, to appropriately diagnosis EM, the clinician must understand numerous biochemical pathways and their interrelationships. Fortunately, approaching a suspicious illness in a newborn based on even a limited knowledge of biochemistry and metabolic laboratory studies can lead to effective diagnostic testing and management. The recognition of a neonate with EM can be accomplished using an organized and rational approach based on diagnostic algorithms presented in this review. When a newborn presents acutely with signs of an EM, appropriate therapy needs to be initiated rapidly due to the high risk of morbidity and mortality. Thus, EM must be considered concurrently in the differential diagnosis that includes the more common disease processes. Increasingly, disorders of metabolism are being managed successfully with acceptable outcomes. Appropriate therapy, in many cases, can result in prevention of mental retardation and death.

It is the purpose of this review to provide an outline for an approach to the evaluation of a newborn suspected of having an EM. In addition, the major clinical and laboratory findings of EMs presenting during the neonatal period will be reviewed. A limited discussion of treatment will focus on the stabilization and acute management of newborns with EM. The discussion will be limited to those EM that present during this early period of life, rather than later during infancy, childhood, or adulthood. Detailed biochemical pathways of EMs are not provided. More comprehensive discussions of each of these topics can be found in recent editions of reference textbooks.[2,3,4]

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