We reviewed 44 symptomatic children tested for CAG repeat expansions in the gene responsible for Huntington's disease (HD). Thirty-three patients had CAG repeat expansions, and 11 did not. No patient with a CAG repeat expansion had a negative family history of HD. Of the 15 patients presenting in the first decade, 12 had greater than 80 CAG repeats and a clinical profile at the time of the test that included two or more of the following:

• declining school performance,
• seizures,
• oral motor dysfunction,
• rigidity,
• gait disorder.

Three patients with smaller CAG repeat expansions had incomplete or atypical symptom profiles.

Symptom patterns in patients presenting in the second decade were more varied but usually included behavioral and motor symptoms.

Patients without CAG expansions had incomplete or atypical symptom profiles.

We define the historical and clinical profiles of HD presenting in the first two decades and suggest that physicians exercise restraint in using a "diagnostic" gene test for HD in the evaluation of at-risk children with incomplete or atypical symptom profiles or no family history of HD, in whom test results are very likely to be normal or unrelated to the patient's symptoms.

Source: Neurology 1997 Oct; 49(4):1048-1053. Nance MA

In order to discover whether laboratories have policies regarding the testing of unaffected children, we surveyed all laboratories registered with Helix, a national net-work of DNA diagnostic laboratories.

Of 186 laboratories asked to respond anonymously to a four-page questionnaire, 156 (84%) replied. A screening question removed 51 laboratories that provided no clinical services.

Of the remaining 105, 92% said that their requisition forms asked the person's age. Substantial minorities had policies for the testing of minors for late-onset disorders (46%), for carrier status for recessive disorders (33%), or for disorders for which the test offers no medical benefit within 3 years (33%).

Most laboratories are responsive to parental requests.

For 12 of 13 late-onset disorders, the majority of laboratories that offered testing had had requests to test children. The majority had tested healthy children, <12 years of age, for eight disorders. Approximately 22% had tested children, <12 years of age, for Huntington disease.

Majorities had received requests to test healthy children for carrier status for 10 of 15 recessive or X-linked disorders and had tested children, <12 years of age, for 6 of these disorders, including cystic fibrosis, hemophilia A, fragile X syndrome, and Duchenne muscular dystrophy.

Approximately 45% of the laboratories occasionally had provided tests directly to consumers.

In view of the possibility that the harms of presymptomatic diagnoses of children sometimes may outweigh the benefits, our results suggest a need for consistent laboratory policies designed for the best interests of the child and the family.

Source: Am J Hum Genet 1997 Nov;61(5):1163-1168. Wertz DC, et al.