In this article I shall discuss the usefulness of the long-wavelength ultraviolet light emitted by the Wood's light in the diagnosis of several forms of porphyria.
The porphyrias are a group of disorders due to abnormalities in the production of the protoporphyrin part of the heme molecule ( heme = protoporphyrin + iron). In all forms of the disease, excessive amounts of one or more of the various precursors of protoporphyrin or of protoporphyrin itself are produced.
In acute intermittent porphyria, which is characterized by neurological complaints, the earliest precursors ( δ-aminolevulinic acid and porphobilinogen) are excreted in the urine. These compounds have not yet become porphyrins and do not fluoresce. The patients are not sensitive to sunlight.
All other forms of porphyria are characterized by sun sensitivity and the presence of porphyrin compounds in serum and tissues in elevated amounts. Porphyrins absorb long-wavelength ultraviolet light (4,000 Angstrom) and emit light of a longer
Halprin KM. Diagnosis With Wood's Light: II. The Porphyrias. JAMA. 1967;200(6):460. doi:10.1001/jama.1967.03120190086015
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