With several hundred diseases and an aggregate frequency of 1 in 600 births, a completediscussion of metabolic disorders is beyond the scope of this book. The classicreference of Scriver et al. (2001) provides an encyclopedic and detailed description ofinborn errors of metabolism. Selected here are several of the more common diseasesthat illustrate the role of generalists in the care of patients with metabolic disorders.Since the focus of this book is congenital malformations, emphasis is given to disordersthat produce alterations in appearance and/or morphogenesis. From the standpointof morphogenesis, these are metabolic dysplasias in the sense that they causealtered histiogenesis (see Chapter 1). Examples include the glycogen-storage diseases(“cherubic” facies and hepatomegaly), the mucopolysaccharidoses (coarsened facewith dysostosis multiplex), and a variety of neuromuscular diseases with hypotonicfacies (bitemporal hollowing, down-turned corners of the mouth) with other malformations(e.g., brain anomalies, limb defects, hepatorenal disease, and contracturesthat can occur in the Smith–Lemli–Opitz or Zellweger syndromes).
Most patients with inborn errors of metabolism will require consistent input frommetabolic specialists for monitoring of injurious metabolites, dietary counseling,and prognostication. Ideally, the primary physician would coordinate general healthcare issues including growth, development, and school issues, leaving metabolicmanagement to the specialist. In practice, the sweep of managed care may forcemany primary physicians to coordinate more of the dietary and metabolic managementof patients with inborn errors of metabolism.