Organic aciduria

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Organic acidurias are a class of inherited metabolic diseases characterized by urinary excretion of abnormal amounts or types of organic acids. There are many of these congenital disorders. They vary in their seriousness from trivial to lethal. Most of them affect more than one organ system. Some affect central nervous system development, causing developmental delay. Some affect physical growth. Some cause episodic illnesses with vomiting and metabolic acidosis; some of these may be precipitated by prolonged fasting, minor viral infections, or any other catabolic state. Some are associated with hypoglycemia and ketosis or ketoacidosis.

Most of the organic acidoses result from defective autosomal genes for various enzymes important to intermediary metabolism. Typically, most of the harm is caused by an impaired ability to synthesize an essential substance or by toxicity to specific organs from excessive amounts of a specific metabolite. Most are inherited as autosomal recessive diseases.

The diagnosis is usually made by detecting an abnormal pattern of organic acids in a urine sample by tandem mass spectrometry. In some conditions, the urine is always abnormal, in others the characteristic substances are only present intermittently. Many of the organic acidurias are detectable by newborn screening with tandem mass spectrometry.

Treatments of organic acidurias vary. There are no effective treatments for some of the conditions. Treatments for some of the others may include avoidance of fasting, extra carbohydrates during illness, or intravenous fluid and dextrose to reverse catabolism. Some can be ameliorated with extra vitamins or other metabolic substrates.