摘要：Abstract Dihydrolipoamide dehydrogenase deficiency, also known as maple syrup urine disease (MSUD) type III, is caused by the deficiency of the {E3} subunit of branched chain alpha-ketoacid dehydrogenase (BCKDH), α-ketoglutarate dehydrogenase (αKGDH), and pyruvate dehydrogenase (PDH). {DLD} deficiency variably presents with either a severe neonatal encephalopathic phenotype or a primarily hepatic phenotype. As a variant form of MSUD, it is considered a core condition recommended for newborn screening. The detection of variant {MSUD} forms has proven difficult in the past with no asymptomatic {DLD} deficiency patients identified by current newborn screening strategies. Citrulline has recently been identified as an elevated dried blood spot (DBS) metabolite in symptomatic patients affected with {DLD} deficiency. Here we report the retrospective {DBS} analysis and second-tier allo-isoleucine testing of 2 {DLD} deficiency patients. We show that an elevated citrulline and an elevated allo-isoleucine on second-tier testing can be used to successfully detect {DLD} deficiency. We additionally recommend that {DLD} deficiency be included in the “citrullinemia/elevated citrulline” {ACMG} Act Sheet and Algorithm.
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