erythropoietic protoporphyria

erythropoietic protoporphyria n a rare porphyria usu. appearing in young children and marked by excessive protoporphyrin in red blood cells, blood plasma, and feces and by skin lesions resulting from photosensitivity

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(EPP) an autosomal dominant disorder due to mutation in the FECH gene (locus: 18q21.3), which encodes ferrochelatase, causing a partial deficiency of the enzyme; it is characterized by increased levels of protoporphyrin in the erythrocytes, plasma, liver, and feces and a wide variety of photosensitive skin changes, ranging from a burning or pruritic sensation to erythema, plaquelike edema, and wheals. The disorder is generally classified as an erythropoietic porphyria, but in classification schemes that include also the category erythrohepatic porphyria, it is classified there.

Erythropoietic protoporphyria. (A), Brownish-black deposits of protoporphyrin in hepatocytes, canaliculi, Kupffer cells, and ductules (H & E stain). (B), Birefringence of deposits, with a Maltese cross configuration of red birefringence in larger deposits (polarized light).