RESUMO
Methylacetoacetyl-CoA thiolase deficiency (T2 deficiency) is a rare congenital and metabolic disease affecting the ketone body and isoleucine metabolism. The typical symptoms are refractory metabolic acidosis, in which large amounts of 2-methyl-3-hydroxybutyry1 carnitine, 2-methyl-3-hydroxybutyrate and tiglylglycine are often detected in the blood and urine. We herein describe an atypical case of T2 deficiency with a high level of 3-hydroxybutyrate and a low level of 2-methyl-3-hydroxybutyrate in the urine. Such a case was diagnosed by urinary organic analysis in combination with gene mutation evaluation. Organic acids in the urine were measured using a gas chromatography mass spectrometer and all exons were sequenced via deep sequencing. Molecular biology analysis confirmed the presence of a homozygous mutation in the acetyl-CoA acetyltransferase 1 (ACAT1) gene. The patient received a special diet of deeply hydrolyzed protein milk powder and raw corn starch. She was followed about 6 months. There were no ketoacidotic episodes and hypoglycemia even when she had fever. In conclusion, patients with atypical features of T2 deficiency should also be investigated early. Gas chromatography mass spectrometry and next-generation full exome sequencing may be helpful in diagnosis.