Clinical biochemical genetics in the twenty-first century.

Abstract

Genetic disorders are recognized to play an increasing role in pediatrics. Close to 10% of diseases among hospitalized children have been ascribed to Mendelian traits inherited as single gene defects, not a surprising figure considering that approximately 1000 inborn errors of metabolism (IEM) have been identified to date, primarily through the detection of endogenous metabolites abnormally accumulated in biological fluids and tissues. The laboratory discipline that covers the biochemical diagnosis of IEM is known as clinical biochemical genetics, and is defined as one concerned with the evaluation and diagnosis of patients and families with inherited metabolic disease, monitoring of treatment, and distinguishing heterozygous carriers from non-carriers by metabolite and enzymic analysis of physiological fluids and tissues. The biochemical genetics laboratory differs from the clinical chemistry laboratory in the extent of interpretation necessary to make its results meaningful to the clinician. While dramatic advances in molecular genetics have greatly changed the landscape of diagnostic options for many genetic disorders, a biochemical approach remains the dominant force for the diagnosis and monitoring of IEM. Owing to the stereotypical clinical presentation of many of these disorders, a major role of the biochemical genetics laboratory is to analyze ever more complex metabolic profiles to reach a preliminary diagnosis, which then needs to be confirmed by enzymic and/or molecular studies in vitro. Accordingly, the role of biochemical genetics in the pediatric practice of the 21st century is to provide a multicomponent screening process that can be divided into four major components: (i) at-risk screening (prenatal diagnosis); (ii) newborn screening (testing of presymptomatic patients); (iii) high-risk screening (testing of symptomatic patients); and (iv) postmortem screening (metabolic autopsy). The focus of our laboratory is to apply state-of-the-art technology such as tandem mass spectrometry to bring as many as possible IEM within the boundaries of newborn screening programs, and to investigate the role played by individual disorders in maternal complications of pregnancy, pediatric acute/fulminant liver failure, and sudden and unexpected death in early life.