Beta‐ketothiolase deficiency: A case with unusual presentation of nonketotic hypoglycemic episodes due to coexistent probable secondary carnitine deficiency

Abstract Beta‐ketothiolase (T2, mitochondrial acetoacetyl‐CoA thiolase) deficiency is an autosomal recessive disorder of isoleucine catabolism and ketone body metabolism that is characterized by increased urinary excretion of 2‐methylacetoacetate, 2‐methyl‐3‐hydroxybutyrate, and tiglylglycine. Most patients with T2 deficiency develop their first severe ketoacidotic events between 5 and 24 months of age. We encountered a case of T2 deficiency who developed the first hypoglycemic crisis without ketosis during her neonatal period and repeated such nonketotic hypoglycemic crisis during her infancy and early childhood. This is a very atypical clinical phenotype in T2 deficiency. We finally realized that she also has severe carnitine deficiency which might suppress beta‐oxidation resulting in nonketotic hypoglycemia. After carnitine supplementation, she actually developed episodes with ketonuria. Her carnitine deficiency was probably a secondary deficiency which is rare in T2 deficiency but if present, may modify the clinical manifestation of T2 deficiency from ketoacidotic events to hypoketotic hypoglycemic events.