Outcome of the first 3-years of a DNA-based neonatal screening program for glutaric acidemia type 1 in Manitoba and northwestern Ontario, Canada.

Glutaric acidemia type 1 (GA1) is overrepresented in the aboriginal population of Island Lake, Manitoba, and northwestern Ontario who speak the Ojibway-Cree (Oji-Cree) dialect. The carrier frequency in these communities has been predicted to be as high as 1 in 10 individuals. Prior to beginning newborn screening for GA1 in May 1998, 18 of 20 affected patients diagnosed at this center have been from these high-risk communities. Most have followed an acute encephalopathic course with permanent neurologic sequelae and high mortality. They excrete small amounts of glutaric acid and 3-hydroxyglutaric acid and have significant residual enzyme activity. A single homozygous mutation in glutaryl-CoA-dehydrogenase (GCDH IVS-1 + 5g right arrow t) has been identified in this population. DNA-based newborn screening targeted to our high-risk communities was begun in order to provide presymptomatic detection and treatment of affected patients. Of the first 1176 newborns screened, 4 affected infants were identified and treated with a low-protein diet, carnitine, and riboflavin. All 4 infants have required numerous hospitalizations for treatment of intercurrent illnesses. Eventually, 3 infants presented with acute dystonic encephalopathy and seizures along with permanent neurological sequelae. One of these infants died unexpectedly at home at 18 months of age. The fourth, now 9 months old, has had a gastrostomy tube placed to facilitate fluid replacement in addition to a standard treatment protocol and is doing well. The reasons for our initial disappointing outcomes in the first 3 of 4 affected babies are likely multiple. Based on our early experience and that of other centers screening newborns for GA1, current therapeutic strategies may be insufficient in preventing the occurrence of neurologic sequelae in some children. An incomplete understanding of the neurotoxic mechanisms underlying this devastating disorder hampers effective management.