Think Metabolic Error in Cases of Near-Miss SIDS

NEW YORK — If a child presents in the emergency department with near-miss sudden infant death syndrome or with a Reye's syndrome-like illness, one should consider the possibility of an inborn error of metabolism, Dr. Joan Shook said at a meeting sponsored by the American College of Emergency Physicians.

In particular, think of medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency, which is the most common of the inherited errors of fatty acid metabolism. If the condition goes undiagnosed, it carries a mortality of 25%, she said. MCAD is a mitochondrial enzyme essential for the β-oxidation of medium-chain fatty acids, a process that is required for energy production during fasting.

The pattern of inheritance seen with MCAD deficiency is autosomal recessive, so it's even worth thinking about in cases of full SIDS, because of the clear implications for future children in that family, she said.

The acute illness typically is characterized by vomiting and lethargy in a child 3–15 months of age, said Dr. Shook, professor of pediatrics and head of the section of emergency medicine, Baylor College of Medicine, Houston.

Laboratory tests, including a metabolic work-up, should be ordered promptly. Findings may include hypoketotic hypoglycemia, hyperammonemia, and an increased anion gap. Liver function tests are likely to be elevated.

Triggers for the acute Reye's-like crisis can include a febrile illness or a metabolic stressor such as fasting, surgery, and alcohol consumption. The acute illness can evolve into seizures, coma, cardiac arrest, and death.

Therapeutic measures during the acute episode include prompt rehydration and correction of hypoglycemia, and should address any identifiable stressors. During the acute episode, it's important to obtain urine and plasma, which can be frozen for further investigation, Dr. Shook said.

If the patient's clinical condition deteriorates and death appears imminent, then one should also consider obtaining skin specimens from the undersurface of the arm and the anterior surface of the thigh for later fibroblast culturing and genetic analysis, she said, noting that consent from the family is needed for this.

It is now recognized that many inborn errors of metabolism were likely misdiagnosed as Reye's syndrome before they were identified during the 1980s, and the incidence of Reye's syndrome has markedly diminished since their recognition. “A review of charts in children with Reye's would likely show that 10%–13% were, in fact, MCAD deficiency.”

Neonatal screening for MCAD deficiency is not mandatory in all states, but this may change with further recognition that the disease's morbidity and mortality can be lowered by long-term measures, such as avoidance of catabolism and aggressive resuscitation during acute crises.

Information about screening for MCAD and other inborn metabolic errors can be found at http://genes-r-us.uthscsa.edu

NEW YORK — If a child presents in the emergency department with near-miss sudden infant death syndrome or with a Reye's syndrome-like illness, one should consider the possibility of an inborn error of metabolism, Dr. Joan Shook said at a meeting sponsored by the American College of Emergency Physicians.

In particular, think of medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency, which is the most common of the inherited errors of fatty acid metabolism. If the condition goes undiagnosed, it carries a mortality of 25%, she said. MCAD is a mitochondrial enzyme essential for the β-oxidation of medium-chain fatty acids, a process that is required for energy production during fasting.

The pattern of inheritance seen with MCAD deficiency is autosomal recessive, so it's even worth thinking about in cases of full SIDS, because of the clear implications for future children in that family, she said.

The acute illness typically is characterized by vomiting and lethargy in a child 3–15 months of age, said Dr. Shook, professor of pediatrics and head of the section of emergency medicine, Baylor College of Medicine, Houston.

Laboratory tests, including a metabolic work-up, should be ordered promptly. Findings may include hypoketotic hypoglycemia, hyperammonemia, and an increased anion gap. Liver function tests are likely to be elevated.

Triggers for the acute Reye's-like crisis can include a febrile illness or a metabolic stressor such as fasting, surgery, and alcohol consumption. The acute illness can evolve into seizures, coma, cardiac arrest, and death.

Therapeutic measures during the acute episode include prompt rehydration and correction of hypoglycemia, and should address any identifiable stressors. During the acute episode, it's important to obtain urine and plasma, which can be frozen for further investigation, Dr. Shook said.

If the patient's clinical condition deteriorates and death appears imminent, then one should also consider obtaining skin specimens from the undersurface of the arm and the anterior surface of the thigh for later fibroblast culturing and genetic analysis, she said, noting that consent from the family is needed for this.

It is now recognized that many inborn errors of metabolism were likely misdiagnosed as Reye's syndrome before they were identified during the 1980s, and the incidence of Reye's syndrome has markedly diminished since their recognition. “A review of charts in children with Reye's would likely show that 10%–13% were, in fact, MCAD deficiency.”

Neonatal screening for MCAD deficiency is not mandatory in all states, but this may change with further recognition that the disease's morbidity and mortality can be lowered by long-term measures, such as avoidance of catabolism and aggressive resuscitation during acute crises.

Information about screening for MCAD and other inborn metabolic errors can be found at http://genes-r-us.uthscsa.edu

NEW YORK — If a child presents in the emergency department with near-miss sudden infant death syndrome or with a Reye's syndrome-like illness, one should consider the possibility of an inborn error of metabolism, Dr. Joan Shook said at a meeting sponsored by the American College of Emergency Physicians.

In particular, think of medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency, which is the most common of the inherited errors of fatty acid metabolism. If the condition goes undiagnosed, it carries a mortality of 25%, she said. MCAD is a mitochondrial enzyme essential for the β-oxidation of medium-chain fatty acids, a process that is required for energy production during fasting.

The pattern of inheritance seen with MCAD deficiency is autosomal recessive, so it's even worth thinking about in cases of full SIDS, because of the clear implications for future children in that family, she said.

The acute illness typically is characterized by vomiting and lethargy in a child 3–15 months of age, said Dr. Shook, professor of pediatrics and head of the section of emergency medicine, Baylor College of Medicine, Houston.

Laboratory tests, including a metabolic work-up, should be ordered promptly. Findings may include hypoketotic hypoglycemia, hyperammonemia, and an increased anion gap. Liver function tests are likely to be elevated.

Triggers for the acute Reye's-like crisis can include a febrile illness or a metabolic stressor such as fasting, surgery, and alcohol consumption. The acute illness can evolve into seizures, coma, cardiac arrest, and death.

Therapeutic measures during the acute episode include prompt rehydration and correction of hypoglycemia, and should address any identifiable stressors. During the acute episode, it's important to obtain urine and plasma, which can be frozen for further investigation, Dr. Shook said.

If the patient's clinical condition deteriorates and death appears imminent, then one should also consider obtaining skin specimens from the undersurface of the arm and the anterior surface of the thigh for later fibroblast culturing and genetic analysis, she said, noting that consent from the family is needed for this.

It is now recognized that many inborn errors of metabolism were likely misdiagnosed as Reye's syndrome before they were identified during the 1980s, and the incidence of Reye's syndrome has markedly diminished since their recognition. “A review of charts in children with Reye's would likely show that 10%–13% were, in fact, MCAD deficiency.”

Neonatal screening for MCAD deficiency is not mandatory in all states, but this may change with further recognition that the disease's morbidity and mortality can be lowered by long-term measures, such as avoidance of catabolism and aggressive resuscitation during acute crises.

Information about screening for MCAD and other inborn metabolic errors can be found at http://genes-r-us.uthscsa.edu