Porphobilinogen (PBG) is a precursor in the heme synthesis pathway.

In acute porphyrias, excess PBG accumulates and is excreted in urine.

Clinical uses include:

Diagnosing acute porphyric attacks (AIP, variegate porphyria, hereditary coproporphyria).

Evaluating patients with abdominal pain, neuropsychiatric symptoms, and red/brown urine.

Monitoring patients with known porphyria for recurrence.

Often performed alongside urine δ‑aminolevulinic acid (ALA), plasma porphyrins, and genetic testing for confirmation.

Analyte: Porphobilinogen in urine (qualitative or quantitative).

Normal Result: Negative or very low levels.

Abnormal Findings:

Positive/High PBG: Indicates acute porphyria, especially during symptomatic attacks.

False negatives: May occur if urine is collected outside of an acute episode.

Clinical Use:

Provides a direct biochemical marker for acute porphyrias.

Helps guide diagnosis, treatment, and monitoring of porphyric disorders.

Supports hematology, neurology, and internal medicine evaluations.