MRI, clinical, and biochemical features of partial pyruvate carboxylase deficiency.

We report a boy with a partial deficiency of pyruvate carboxylase as documented in enzyme assays of skin fibroblasts, lymphocytes, and hepatic tissue. Magnetic resonance imaging at age 20 months demonstrated a leukodystrophic process involving the brain stem and subcortical white matter, which, except for the brain stem, improved after biotin treatment. The lymphocyte pyruvate carboxylase activity of both heterozygous parents slightly increased after receiving oral biotin for 1 month, but a definitive enzymatic response to biotin was not confirmed in our patient. At age 6 years, he is dysarthric with a spastic quadriparesis despite improvements in development and myelination. This is the first demonstration of magnetic resonance imaging changes in this disease.