To the Editor.—
Attempts have been made by several groups to assess the photosensitivity of patients with erythropoietic protoporphyria (EPP) by an objective method, ie, phototesting with monochromatic light at several discrete wavelengths. However, many patients have failed to respond at all to this kind of light exposure. We have had more consistent phototest results by irradiating with polychromatic light ranging from 380 to 560 nm and by grading the immediate erythema that developed.1 We suggest that phototesting with this spectral region, as well as with monochromatic light, be used as an objective method of evaluating photosensitivity in EPP, as well as a response to therapy.When we phototested patients with EPP using a xenon arc lamp filtered to transmit 380 to 560 nm,1 immediate erythema developed in every patient tested who was exposed to this light. In addition to erythema, wheals, itching, and burning develop in a
Mathews-Roth MM, Kass EH, Fitzpatrick TB, Pathak MA, Harber LC. Phototesting as an Objective Measure of Improvement in Erythropoietic Protoporphyria. Arch Dermatol. 1979;115(12):1391–1392. doi:https://doi.org/10.1001/archderm.1979.04010120001002
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