To the Editor: I would certainly agree with most of Dr. Koch's comments on my paper. In particular, I appreciate his emphasis on the inadequacy of a plain IQ for evaluation of developmental damage. The reports of psychometric evaluation of treated PKU patients need to be much more detailed if we are to compare results, and at the same time learn something of the nature of the damage produced by this metabolic disorder.
I would also agree that hyperactivity and short attention span have interfered with the learning potential of my patients, and I was very interested in the patient report in Dr. Koch's letter. My first case did not develop as high a serum phenylalanine upon return to a full diet (27 mg% four months after stopping diet control), but the level may have risen since then, and I am planning a repeat study and trial on diet control