Inborn metabolic errors, while not common, may have significant implic
ations for patients. Those patients with such errors who have acute li
fe-threatening symptoms must be treated immediately, and specimens for
analysis should best be obtained during the critical stage. Many infa
nts and children seen with acute symptoms are the ones most likely to
have treatable diseases. At a more leisurely pace, other inborn errors
can be diagnosed in order to provide appropriate counseling and progn
osis.