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.