Findings | Maple syrup urine disease | Organic acidemias | Urea cycle defects | Disorders of carbohydrate metabolism | Fatty acid oxidation disorders | Mitochondrial disorders | Peroxisomal disorders | Lysosomal storage disorders |
Metabolic acidosis | ± | ++ | – | ± | ± | ± | – | – |
Respiratory alkalosis | – | – | + | – | – | – | – | – |
Hyperammonemia¶ | ± | + | ++ | – | ± | – | – | – |
Hypoglycemia | ± | ± | – | + | + | ± | – | – |
Ketones | A/H | H | A | A/H | A/L | A/H | A | A |
Lactic acidosis | ± | ± | – | + | ± | + | – | – |
–: usually absent; ±: sometimes present; +: usually present; ++: always present; A: appropriate production of ketones for the degree of hypoglycemia (eg, ketones are appropriately absent in peroxisomal disorders because hypoglycemia is not a feature of these disorders); H: inappropriately high (eg, 4+ ketones are inappropriately high in the setting of a normal glucose level); L: inappropriately low (eg, ketones are inappropriately low if the blood glucose is <20 mg/dL and the urine ketones are only 1+ or 2+ because they should be significantly elevated in the setting of such extreme hypoglycemia).
* Within disease categories, not all diseases have all findings; for disorders with episodic decompensation, clinical and laboratory findings may be present only during acute crisis; for progressive disorders, findings may not be present early in the course of disease.
¶ Improper collection, sample mishandling, and delay in analysis can result in spuriously elevated ammonia levels. An ammonia specimen should be obtained from a free-flowing (no tourniquet) venous specimen, the test tube should immediately be placed on ice, and the sample should analyzed within 30 minutes.Do you want to add Medilib to your home screen?