Urinary porphobilinogen (PBG) measurement evaluates porphyrias, such as acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria.
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Quantitative measurements of porphobilinogen, total urinary porphyrins, and aminolevulinic acid may help determine the different forms of porphyria.
Porphyrins are a group of genetic disorders associated with deficiencies of various enzymes involved in either the synthesis of porphyrin or its metabolism. Porphyrins (uroporphyrins and coproporphyrins) and porphobilinogen are essential building blocks in heme synthesis. Heme is a constituent of the red blood cell hemoglobin. In most forms of porphyria, there are elevated levels of porphyrins and porphobilinogen in the urine. Porphyrias are typically classified as erythropoietic or hepatic based on the location of the defective enzyme. In addition, hepatic porphyria can be further classified as chronic or acute based on their clinical manifestations.
Acute hepatic porphyrias, i.e., acute intermittent porphyria, hereditary porphyria, and variegate porphyria, are associated with symptoms that usually begin in adolescence or later. Frequent symptoms include severe abdominal pain, peripheral neuropathy, and psychiatric symptoms. Many medications, alcohol, infections, hunger, heavy metals, and hormonal changes can cause seizures.
Possible Interpretations of Pathological Values
- Increase: Porphyria, liver disease, lead poisoning, pellagra
- Decrease: No clinical significance
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