The clinical chemistry of the porphyrias

Biochemical differentiation of the porphyrias

OBJECTIVES

To differentiate the porphyrias by clinical and biochemical methods.

DESIGN AND METHODS

We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.

Ion exchange analysis of porphyrins in urine

An easy and cheap analysis of total prophyrin in urine is described based on the ion exchange resin Dovex 2 X 8, 50--100 mesh. Recovery of added porphyrin varied between 65 and 90% for uro- and 70 and 95% for coproporphyrin. The use of the method with internal standard is described and exemplified. Ammoniacal solutions of crystalline free porphyrins were used as standards.