Beta-ketothiolase deficiency with progressive basal ganglia and extra basal ganglia involvement: CT-MRI correlation in a pediatric metabolic encephalopathy: A case report.

Beta-ketothiolase deficiency (BKTD), also called mitochondrial acetoacetyl-CoA thiolase (T2) deficiency, is a rare autosomal recessive inborn error of metabolism affecting isoleucine catabolism and ketone body utilization. Although recurrent ketoacidotic crises are the hallmark of the disease, neurological complications-particularly basal ganglia injury-are increasingly recognized. We report a 2-year-old girl with known BKTD who presented with severe euglycemic ketoacidosis and acute encephalopathy. Initial CT showed symmetric hypodensity confined to the bilateral globus pallidi. Follow-up CT during ongoing metabolic instability demonstrated interval progression to involve the bilateral putamina and cerebral peduncles. MRI, obtained after referral, revealed nonenhancing T2/FLAIR hyperintense, T1 hypointense globus pallidus lesions without diffusion restriction but with punctate SWI hypointensities consistent with microcystic cavitary degeneration and microhemorrhage. There were additional diffusion-restricting lesions in the bilateral cerebral peduncles, small nonrestricting white matter foci in the frontal and right parietal lobes, and generalized cerebral atrophy. A baseline MRI 17 months earlier had been normal. This case illustrates the evolution from acute pallidal injury to irreversible basal ganglia necrosis with microhemorrhage and concurrent acute/subacute tract involvement, and highlights how CT and MRI together can characterize the spectrum of BKTD-related brain injury.