Pediatric mitochondrial respiratory chain disorders in the Centro region of Portugal.

The present study reviewed mitochondrial respiratory chain disorders diagnosed at the sole tertiary pediatric hospital in the Centro region of Portugal and estimated incidence and prevalence in this region. The Bernier criteria were used to retrospectively classify 200 children investigated from 1997 to 2006. A total of 78 patients were assigned with definite primary mitochondrial disorder, two thirds presenting in the first year of life. At presentation, 61 children had neuromuscular symptoms. Neurologic, ophthalmologic, growth retardation, muscular, cardiac, respiratory, hepatic, hematologic, and digestive symptoms were the most frequent clinical features. A classic mitochondrial syndrome was identified in 12 children, 6 of them with Leigh syndrome. Major respiratory chain enzymatic defects were detected in 73 cases. Pathogenic mitochondrial DNA or nuclear DNA mutations (or both) were observed in 9 children. Mortality was 29.5%, with median age of death at 8 months. Survival was shorter for patients with onset at infancy or children with liver or cardiac involvement, or with lactic acidosis. Estimated incidence of mitochondrial disorders in children less than 10-years-old was 1.5/10,000, and point prevalence was 5.4/100,000, respectively. These disorders seem to have a high incidence and poor prognosis in the Centro region of Portugal.