Inborn errors of metabolism: Metabolic emergencies
- V Reid Sutton, MD
V Reid Sutton, MD
- Professor of Molecular and Human Genetics
- Baylor College of Medicine
Congenital metabolic disorders result from the absence or abnormality of an enzyme or its cofactor, leading to either accumulation or deficiency of a specific metabolite (table 1 and table 2 and table 3 and table 4 and table 5 and table 6).
The presenting features of inborn errors of metabolism (IEM) may be acute or chronic. Acute signs include episodic vomiting accompanied by dehydration or shock, lethargy and coma, rhabdomyolysis, and hypoglycemia associated with minor illnesses, stress, or a prolonged fast. Chronic signs of metabolic disease include growth delay/failure to thrive (FTT), hepatomegaly, cardiomyopathy, spastic diplegia, and developmental delay or regression.
Optimal outcome for children with IEM depends upon recognition of the signs and symptoms of metabolic disease, prompt evaluation, and referral to a center familiar with the evaluation and management of these disorders . Delay in diagnosis may result in acute metabolic decompensation, progressive neurologic injury, or death.
This topic provides an overview of the presentation, initial evaluation, and management of children with suspected IEM who present with acute metabolic decompensation. Confirmation of diagnosis of specific disorders typically requires specialized testing and should be undertaken in consultation with a specialist in genetics or metabolic diseases. Determination of the specific IEM is reviewed separately. The classification and most common chronic presentations of IEM are also discussed separately, as are individual disorders. (See "Inborn errors of metabolism: Classification" and "Inborn errors of metabolism: Epidemiology, pathogenesis, and clinical features" and "Inborn errors of metabolism: Identifying the specific disorder".)
CAUSES OF ACUTE METABOLIC DECOMPENSATION
Inborn errors of metabolism (IEM) can be grouped into disorders of intermediary metabolism (classic IEM), disorders of biosynthesis and breakdown of complex molecules, and disorders of neurotransmitter metabolism (table 1). Many of the disorders of intermediary metabolism can present with acute, life-threatening illness, particularly organic acidurias, urea cycle disorders, maple syrup urine disease, and fatty acid oxidation disorders. Neurotransmitter defects and related disorders can present with severe metabolic encephalopathy. In contrast, the disorders involving complex molecules tend to progress more slowly and do not typically cause acute metabolic decompensation. (See "Inborn errors of metabolism: Classification", section on 'Classification'.)To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
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- CAUSES OF ACUTE METABOLIC DECOMPENSATION
- CLINICAL PRESENTATIONS
- Lethargy and coma
- SIDS or ALTE
- LABORATORY FINDINGS
- Acid-base disorders
- INITIAL EVALUATION
- EVALUATION OF SPECIFIC CRITICAL PRESENTATIONS
- Acid-base disorder
- SIDS and ALTE
- DIFFERENTIAL DIAGNOSIS
- IMMEDIATE MANAGEMENT
- Supportive measures
- Provision of cofactors