The porphyrias are a group of diseases associated with hereditary and acquired deficiencies in the biosynthetic pathway of heme. The laboratory diagnosis of porphyrin disorders rests primarily with the identification of patterns of porphyrin intermediates. Multiple species have been identified for each of the porphyrins based on the order of their substitutions. Porphyrias are disorders of porphyrin metabolism caused by specific defects of enzymes of the heme biosynthetic pathway. Consequently, each type of porphyria is characterized by the accumulation of the precursor proximal to the step dependent on the defective enzyme. All but two porphyrias (acute intermittent and plumbo-porphyria) are characterized by cutaneous lesions caused by the photosensitizing effects of accumulated porphyrins. Maximal skin reactivity occurs in the 400-410 nm region of the spectrum, known as the Soret band, which corresponds to the wavelengths that porphyrins show the most intense absorption. This assay allows differentiation of three conditions according to their porphyrin content. Variegate porphyria, (VP) is an autosomal dominant disorder associated by a defect in the enzyme protoporphyrinogen oxidase, which catalyzes the last step of heme biosynthesis. These cases present a peak in the spectral area of 626-628 nm. Erythropoietic protoporphyria (EPP) is another autosomal dominant condition that causes acute photosensitivity and is characterized by an increase of plasma protoporphyrin with a characteristic peal at 636 nm. A third group which includes normal subjects, non-porphyria patients, and those suffering from acute intermittent porphyria, hereditary coproporphyria, congenital erythropoietic porphyria (Gunther Disease) and porphyria cutaneous porphyria cutanea tarda.

• Patient should refrain from alcohol consumption for 24 hours prior to collection.
• Patient should be off all medications for 1 week prior to sampling.
  • If this is not possible, note all medications on the sample requisition.

Dk green heparin (Li or Na), no gel

Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times to prevent clotting

PROTECT FROM LIGHT

1. Spin within two (2) hours of sample collection
2. Transfer plasma to a Amber screw-cap polypropylene frozen transport tube/vial - 4mL (LabCorp), labelled as the appropriate plasma type

Amber screw-cap polypropylene frozen transport tube/vial - 4mL (LabCorp)

Frozen, protected from light

• Gel-barrier tubes will be rejected

Extraction and Scanning Spectrofluorometry

Total porphyrins:          0.1 – 1.0 µg/dL
Plasma fractionation:    < 1.0 µg/dL
Individual porphyrins:   < 1.0 µg/dL