Peripheral blood film. The blood film from a control subject (A and B) and a patient with erythropoietic protoporphyria (EPP) (C and D) all are wild-type at ABCB6. (A and C) The differential interference contrast (DIC) and fluorescence image are shown as an overlay. (B and D) Only fluorescence is shown. Fluorescent protoporphyrin is visualized by excitation at 405 nm with emission peak at 600 to 650 nm. Protoporphyrin is present in RBCs but not in lymphocytes. PPIX accumulates in EPP erythrocytes, suggesting that ABCB6 does not act as a PPIX exporter.