WBR0986
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 3 year old girl is noted to have progressively worsening hypotonia associated with two previous episodes of acute self resolving ataxia. The girl is on the lower limit of growth in height and weight with a noticeable developmental delay. Laboratory results are significant for mild metabolic acidosis. A skeletal muscle biopsy reveals immunochemical evidence of E1 subunit deficiency in the pyruvate dehydrogenase complex. The parents are genetically counseled and advised to provide the girl with a strict diet. Which of the following amino acids should be included in this girl's diet?]] |
| Answer A | AnswerA::Methionine |
| Answer A Explanation | [[AnswerAExp::Methionine is a strictly glucogenic amino acid. A patient with pyruvate dehydrogenase deficiency is required to have a strict ketogenic diet.]] |
| Answer B | AnswerB::Valine |
| Answer B Explanation | [[AnswerBExp::Valine is a strictly glucogenic amino acid. A patient with pyruvate dehydrogenase deficiency is required to have a strict ketogenic diet.]] |
| Answer C | AnswerC::Isoleucine |
| Answer C Explanation | [[AnswerCExp::Isoleucine is a glucogenic and ketogenic amino acid. A patient with pyruvate dehydrogenase deficiency is required to have a strict ketogenic diet.]] |
| Answer D | AnswerD::Threonine |
| Answer D Explanation | [[AnswerDExp::Threonine is a glucogenic and ketogenic amino acid. A patient with pyruvate dehydrogenase deficiency is required to have a strict ketogenic diet.]] |
| Answer E | AnswerE::Lysine |
| Answer E Explanation | [[AnswerEExp::Lysine and leucine are strictly ketogenic amino acids that do not require pyruvate dehydrogenase for their metabolism. A patient with pyruvate dehydrogenase deficiency is required to have a strict ketogenic diet rich in fat and the amino acids leucine and lysine.]] |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Pyruvate dehydrogenase deficiency is an X-linked disease caused by a mutation in the E1 alpha subunit of the pyruvate dehydrogenase complex leading to metabolic acidosis and neurological symptoms. There are two main types of presentations of pyruvate dehydrogenase deficiency: a metabolic presentation characterized by severe lactic acidosis at birth and a chronic neurological presentation characterized by hypotonia, lethargy and mental retardation. The treatment of this disease is a strict ketogenic diet high in fat and in the ketogenic amino acids lysine and leucine. Pyruvate dehydrogenase is also thiamine responsive.
Educational objective: Pyruvate dehydrogenase deficiency is an X-linked disease caused by a mutation in the E1 alpha subunit of the pyruvate dehydrogenase complex leading to metabolic acidosis and neurological symptoms. The treatment of this disease is a strict ketogenic diet high in fat and in the ketogenic amino acids lysine and leucine. Glucogenic amino acids: methionine, valine Reference: Bindoff, L. A., Birch-Machin, M. A., Farnsworth, L., Gardner-Medwin, D., Lindsay, J. G., Turnbull, D. M. Familial intermittent ataxia due to a defect of the E1 component of pyruvate dehydrogenase complex. J. Neurol. Sci. 93: 311-318, 1989. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Pyruvate dehydrogenase, WBRKeyword::lysine, WBRKeyword::ketongenic |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |