Uroporph,24hr, Urine

Laboratory assay overview

Evaluate porphyrias, including those involving deficiencies of enzymes that are needed for heme synthesis and chemical porphyrias. In congenital erythropoietic porphyria , elevations of urinary uroporphyrin and coproporphyrin occur, with the former exceeding the latter. In acute intermittent porphyria , porphobilinogen and δ-aminolevulinic acid are elevated in acute attacks, and mild increases of urinary uroporphyrin and coproporphyrin may be found. Porphobilinogen is increased in many but not all patients with acute intermittent porphyria in latent periods. Quantitative porphobilinogen is a better test than δ-aminolevulinic acid overall for acute intermittent porphyria, but both are used (as well as the Watson-Schwartz test).1 Coproporphyrin and porphobilinogen excretion in urine are markedly increased during acute attacks of hereditary coproporphyria , increase of urinary uroporphyrin may be found, and increased fecal coproporphyrin III is described. In variegate porphyria in acute attacks, results are similar to those of acute intermittent porphyria. Porphobilinogen and ALA are prone to become normal between attacks. Urine coproporphyrin exceeds uroporphyrin excretion during acute attacks. Chemical porphyrias occur. Porphyrinogenic chemicals include certain halogenated hydrocarbons that cause the excretion of increased uroporphyrin. In lead poisoning elevation of δ-aminolevulinic acid greater than that of porphobilinogen occurs and porphobilinogen may be normal. Urinary coproporphyrin characteristically is increased. Free erythrocyte protoporphyrin is increased. Toxins such as lead interfere with heme synthesis and cause porphyrinuria. Increased urine excretion of uroporphyrinogen, uroporphyrin, and coproporphyrin occurs in porphyria cutanea tarda. It is found in (1) middle-aged men who like ethanol, (2) young women on oral contraceptives, and in (3) subjects on dialysis. These patients do not excrete increased porphobilinogen, but they may have slight elevations of δ-aminolevulinic acid. Two Types of Porphyria*† Cutaneous Porphyria Clinical Notes Neurologic Porphyria Clinical Notes * Note: Low urine values are meaningless. Only greatly increased values (10-15 times the upper limit of the reference interval) have clinical significance for porphyrias. †Timing of urine collection for the investigation of cutaneous porphyria is not as critical as in neurologic porphyrias in which PBG screening test should be collected when the patient is symptomatic. Congenital erythropoietic porphyria (CEP) Very rare; generally diagnosed in childhood Acute intermittent porphyria (AIP) 80% of neurologic porphyrias Protoporphyria (PP) Seen in adolescents Variegate porphyria (VP) Porphyria cutanea tarda (PCT) 90% (most common) of cutaneous porphyrias; seen in middle age Coproporphyria (CP) The accompanying flow diagrams outline steps for the investigation of cutaneous and neurologic porphyrias.