Phosphoenolpyruvate carboxylase deficiency Pyruvate carboxylase deficiency Pyruvate dehydrogenase complex deficiency Succinate dehydrogenase deficiency Peroxisomal disorders Adrenomyeloneuropathy Adrenoleukodystrophy in neonatal, adult Catalase deficiency Glutaric acidemia type III Leber hereditary optic neuropathy Refsum disease infantile, adult Rhizomelic chondrodysplasia punctata Wolfram syndrome Zellweger syndrome Congenital disorders of glycosylation Disorders of metal transport Disorders of heme metabolism Disorders of nucleic acid metabolism Disorders of cholesterol synthesis Disorders of bile acid synthesis Disorders of neurotransmitter metabolism Laboratory Findings In the patient with potentially life-threatening symptoms, evaluation for possible IEM should be initiated immediately The initial laboratory evaluation of a patient with suspected IEM includes electrolytes, glucose, venous blood gas, CBC, ammonia, lactate, blood urea nitrogen (BUN), creatinine, liver tests (aspartate transaminase [AST] and alanine transaminase [ALT], prothrombin time [PT], partial thromboplastin time [PTT]), uric acid and urinalysis If possible, the initial evaluation should also include samples for specialized testing including plasma amino acids, urine organic acids, and acylcarnitine profile ( Table 95.4 ) In addition to these studies, patients with history or physical examination suggestive of myopathy should have lactate dehydrogenase, aldolase, creatinine phosphokinase, and urine myoglobin measured as part of their initial screen If a metabolic disease is suspected, consultation with an IEM specialist should be considered to guide further laboratory evaluation and assist with the appropriate collection and processing of specimens Blood should be collected and sent for plasma amino acids and acylcarnitine profile, while urine should be collected for potential analysis of organic acids, acylglycine, and/or orotic acid ( Table 95.5 ) Additional blood and urine for possible further testing should be obtained and stored Cerebrospinal fluid (CSF), if obtained, should be collected at the same time as plasma and immediately frozen and stored for possible further testing for neurometabolic disorders, most commonly nonketotic hyperglycinemia, disorders of serine biosynthesis, and/or neurotransmitter disorders Measurement of lactate and pyruvate are important components of the ED evaluation but may be difficult to interpret, particularly in the patient with hypoxia, poor perfusion, seizure, and/or sepsis Laboratory abnormalities are often transient, particularly if fluids and/or glucose are administered; therefore, normal values not rule out an IEM It is critical to obtain pretreatment specimens, if possible If pretreatment specimens were not obtained, as is often the case because many IEMs are first suspected based on results of routine laboratory studies,