to the editor: I found the article by Drs. Legler and Rose¹ on the assessment of abnormal growth curves to be quite interesting. One of the most common abnormalities we see in our practice is poor weight gain in children. Legler and Rose recommend that children who have poor weight and height gain and decreased growth of head size undergo laboratory evaluation, including evaluation for inborn errors of metabolism.

I would like to know specifically which tests should be ordered to screen for inborn errors of metabolism and which diseases are common causes of decreased growth.

Is there a reference containing this information that the author could suggest?

in reply: I wish to thank Dr. Spencer for her inquiry concerning the role of inborn errors of metabolism as etiologies of growth failure in children. I would refer Dr. Spencer to a general pediatric reference such as the 20th edition of Rudolph's Pediatrics.¹ In particular, Chapter 6 contains lists and descriptions of the multitude of metabolic disorders that have been described in the literature. Growth retardation (that is, “failure to thrive”) is listed as a potential component in a number of these metabolic disorders. Figure 6–12 outlines a sequence of laboratory studies that may be used to approach this large group of diseases. On the basis of this diagram, the family physician can begin the initial work-up with a complete blood count, serum chemistry profile (to include serum bicarbonate, glucose, liver function tests and bilirubin), serum ketones, serum ammonium and urine reducing substances. Abnormalities in these initial findings lead to further testing with serum and urine metabolic screens. Further specialized testing at referral centers may be required.