Purpose or Case Report: Propionic acidemia is a rare autosomal recessive disorder in which a genetic mutation results in the abnormal function of propionyl co-enzyme A (CoA) carboxylase, an enzyme involved in protein breakdown and lipid catabolsim. This results in the accumulation of metabolites which can have devastating neurologic consequences. The incidence in the United States has been reported as 1 in 100,000 births. The genetic and metabolic factors contributing to this disorder are discussed.
Methods & Materials: Brain MRI findings in propionic acidemia are described in 2 patients. The first patient is a 5-month-old male who was transferred from an outside hospital on respiratory support with severely elevated ammonia and metabolic acidosis. The second patient is a 15-year-old female who presented to the emergency department with a mild headache and increased sleepiness. Following admission, she decompensated significantly, and her serum ammonia level was shown to be three times the normal limit.
Results: MRI of the brain in the first child demonstrated diffusion restriction in a subcortical pattern evenly distributed throughout both cerebral hemispheres. In the second patient, MRI revealed cortical diffusion restriction throughout the entire left cerebral hemisphere, however, the right cerebral hemisphere was affected to a much lesser extent. Interestingly, parenchymal volume loss was prominent throughout the right cerebral hemisphere. The basal ganglia and thalami were not affected in either child. Follow-up MRI obtained in both children after appropriate therapy showed improvement in diffusion restriction. There was diffuse cerebral atrophy on follow-up of the first patient. Follow-up MRI of the second patient showed resolution of diffusion restriction and continued volume loss throughout the contralateral (right) cerebral hemisphere.
Conclusions: These cases illustrate unique and distinct patterns of diffusion restriction in propionic acidemia crises. Commonly reported findings in the literature include involvement of the basal ganglia and/or thalami which were not seen in these two children. The cases shown here further expand the differential diagnosis for nonspecific diffusion restriction and demonstrate uncommon presentations of an already rare disease entity.