Table 51-1 Estimates of Incidence of Various Classes of Disorders Diagnosed or Followed at Specialized Clinics per 100,000 Population* BRITISH COLUMBIA 1969–1996 WEST MIDLANDS 1999–2003
Amino acid disorders 7.5 (excluding phenylketonuria) Lysosomal storage diseases 7.5 19 Phenylketonuria 7.5 12.5 Peroxisomal disorders 3.5 7.5 Mitochondrial diseases 3 4.5 *Populations in British Columbia, Canada (a predominantly white population), between 1969 and 1996, and in the West Midlands of the United Kingdom (which has a diverse ethnic breakdown) between 1999 and 2003.
an organic acid disorder. Similarly specific metabolic disorderspredispose to cardiomyopathy, myopathy, hepatopathy, developmental delay, sepsis and developmental regression; appropriate evaluation should be tailored to the clinical presentation.
Introduction of new foods or metabolic stress associated with fasting or fever may unmask an inborn error of metabolismduring infancy or in older children. The introduction of fructoseor sucrose in the diet may lead to decompensation in hereditaryfructose intolerance. In older children, increased protein intakemay unmask disorders of ammonia detoxification.
Loss of regulation
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Figure 51-1 Depiction of the basic paradigm in inherited disorders of metabolism. Deficiency of an enzyme complex results in accumula-Altered Mental Status tion of metabolites proximal to the blocked metabolism and deficiency Acidemia of the product of the reaction. Sites of genetic control are indicated.
Use of glucose with consequent hypoglycemia oxidation defects
Long-chain fatty acid Fat for energy Long-chain fats Use of glucose with consequent hypoglycemia; oxidation defects mitochondrial dysfunction in liver, heart, etc., leading to organ dysfunction
Glycogen storage disease Glucose to prevent fasting Glycogen resulting in Risk of hypoglycemic brain injury and storage tissue hypoglycemia storage in liver, muscle, heart dysfunction
Ketone utilization Fat for energy Ketones Risk of hypoglycemic brain injury; profound metabolic disorders
Galactose Elevated galactose leads to severe hepatic dysfunction, neurologic injury, and impaired immune response