The diagnosis and management of Mendelian (i.e., single gene) dysmorphic or metabolic syndromes in newborns and children constitutes a major branch of the classical practice of Medical Genetics. Though the care and study of rare diseases in children also is being revolutionized by advances in genetic technologies, Mendelian genetics has long been a mature clinical field. Therefore, even a cursory overview of the accumulated knowledge of the diagnosis and care of Mendelian disorders in children would enormously exceed the scope of this book. Rather, in keeping with its goals, the aim of this and following chapters will be to (1) empower nongeneticist practitioners with a rational approach to the child with a suspected genetic disorder, (2) demystify the typical evaluation of a suspected disorder by a specialist, and (3) describe critical areas of recent or anticipated advancement where the nongeneticist will likely play an increasingly important role in applying genomic technologies to the care of children.
The essential first step whenever a genetic disorder is suspected is to conduct a detailed family history. A proper family history includes at least three generations: the child and all siblings, parents and all their siblings, uncles/aunts and first cousins, and the grandparents. In addition to determining the health of each relative and the cause of any deaths, it is important to ask about miscarriages/stillbirths, developmental delay, seizure disorders, sudden deaths, and mental illness, as these may be subtle manifestations of the condition affecting the patient at hand.
Until the mid-2000s mandatory screening of newborns was highly variable state to state, with some screening as few as six conditions and others screening for dozens of conditions. In 2006, the American College of Medical Genetics and Genomics (ACMG) published a report recommending a standard panel of tests. Today, a minimum of 31 core disorders are tested in all 50 states of the United States. The practitioner should be aware of when diseases were added to the NBS requirements in a particular state to avoid falsely assuming that a child with symptoms of an inborn error of metabolism underwent NBS. As time passes fewer and fewer patients under age 18 will have missed out on NBS. Newborn screening encompasses disorders that are not necessarily genetic, such as hypothyroidism, hearing loss, and congenital heart disease. These are beyond the scope of this text.
Pediatricians seeking extra credit should obtain a list of what conditions are screened in their state, and when each condition was added to the state's panel.
NBS: Collecting and reporting
The precise details of the timing of collection, method of collection, method of analysis, and reporting process vary from state to state and internationally. An excellent resource is http://www.babysfirsttest.org/, which compiles information for parents and professionals regarding the diseases screened, collection and reporting methods, and links ...