endocrine and metabolic disorders
Erythropoietic Protoporphyria and X linked Protoporphyria
Diagnosis
Red blood cell and plasma protoporphyrin measurement Genetic testing forFECHorALAS 2gene mutations Erythropoietic protoporphyria or X-linked protoporphyria should be suspected in children and adults with painful cutaneous photosensitivity who experience no blisters or scarring. Gallstones in children should prompt testing for EPP and XLPP. Family history is usually negative. The diagnosis is confirmed by finding increased red blood cell and plasma protoporphyrin levels. The peak plasma fluorescence occurs at 634 nm, following excitation at 410 nm. Red blood cell protoporphyrin should also be fractionated to determine the proportions of metal-free and zinc protoporphyrin. In EPP, the proportion of red blood cell protoporphyrin that is metal-free is almost always > 85%. The presence of > 15% zinc protoporphyrin suggests XLPP. If measured, plasma coproporphyrin and urinary porphyrin levels are normal. Stool protoporphyrin may be elevated, but coproporphyrin level is normal. Potential carriers among relatives can be identified by finding increased red blood cell protoporphyrin levels and by genetic testing if a mutation has been identified in the index case. 