Neurologic complications of inherited mitochondrial abnormality, and neurologic consequences of inborn errors of metabolism.

The possibility of gene therapy for patients with Menkes or Gaucher's disease has been improved by the isolation of a promising candidate gene and production of a mouse model, respectively. Many mutations of mitochondrial DNA are being associated with mitochondrial encephalomyopathies, and protection of the resultant biochemical deficiency can be achieved with a remarkably low percentage of normal mitochondrial DNA. The correlation between mutation, biochemical deficiency, and neurologic consequence, however, remains frustratingly obscure. Gas chromatography-mass spectrometric urinalysis is becoming increasingly important in the diagnosis of metabolic disorders and is revealing new and unexpected deficiencies.