Inactivation of protoporphyrin IX in erythrocytes in patients with erythropoietic protoporphyria: A new treatment modality.

Abstract

Erythropoietic protoporphyria (EPP) is a rare, genetic disease with reduced ferrochelatase activity causing protoporphyrine IX (PpIX) to accumulate in erythrocytes. PpIX activation by daylight causes skin erythema, edema, burning, and stinging. No treatment exists to reduce PpIX. To introduce a method that reduces PpIX in erythrocytes to relieve skin symptoms in patients with EPP. A case series of 7 patients with EPP constituted this explorative study. Erythrocyte PpIX was inactivated by illuminating the patients' heparinized blood outside their body, then returning it to the patient. About 3 litres of blood was illuminated with 630 nm light, 20 J/cm2. The effect was measured as a reduction in erythrocyte PpIX. The patients reported the number of minutes in daylight tolerated before and after intervention. This procedure reduced PpIX by about 30 % and daylight tolerance was, on average, increased by 14 times. The subsequently excreted photoproducts resulted in some liver toxicity. Three treatments during spring and early summer were sufficient to reduce the patients' symptoms throughout the year in Northern Europe. Extracorporeal erythrocyte photodynamic therapy is the first treatment to successfully reduce the amount of PpIX in the blood of EPP patients, thus "normalizing" their daylight tolerance.