The parents of a 1-year-old boy are alarmed at the increasing frequency of their child biting his lips and finger tips. In addition, on several occasions they have noticed what appears to be "orange sand" in their son's diapers. They report to their pediatrician that they believe their child is delayed in acquiring motor skills such as holding up his head and sitting unaided. Clinical tests performed on serum and urine indicate a 3-fold increase in serum uric acid and a 10-fold elevation in the urinary ratio of uric acid to creatinine. These findings are suggestive of which of the following disorders?

Question

Quizplus · Accepted Answer

The symptoms and test results are indicative of Lesch-Nyhan disease, which is characterized by self-mutilating behaviors, neurological delays, and elevated uric acid levels due to a deficiency in the HGPRT enzyme.  Deficiencies in the purine nucleotide salvage enzyme, HGPRT, cause 3 overlapping clinical syndromes. The most severe deficiency (patients having <1.5% residual enzyme activity) results in debilitating neurologic disability, overproduction of uric acid, and behavioral abnormalities that include impulsive and self-injurious activities such as biting finger tips and lips. This severe form of HGPRT deficiency is referred to as Lesch-Nyhan disease. The overproduction of uric acid leads to symptoms of gout and the appearance of "orange sand" in the urine.

The Parents of a 1-Year-Old Boy Are Alarmed at the Increasing