The cDNA for the human gene has been cloned, and at least eight mutations have been characterized. The most dramatic findings are related to repeated vesiculation, scarring, and mutilation, which follow exposure to sunlight. These late changes may be mistaken for scleroderma. Alopecia, conjunctivitis, and corneal inflammation are additional findings. Bone deformities, attributed to the toxic effects of porphyrin deposition in bone and perhaps to rickets secondary to avoidance of sunlight, are sometimes present.
Hemolytic anemia is common and is often accompanied by splenomegaly.
Hypersplenism with deficiency of platelets may occur. Fluorescence of teeth as well as of red blood cells and their precursors in the blood and bone marrow can be demonstrated by irradiation with the Soret band. As with other photosensitive porphyrias, window glass and conventional ultraviolet sunscreens are ineffective in blocking the offending wavelengths. Suppression of erythropoiesis and therefore heme synthesis can be achieved by transfusion and, when hemolysis is present, by splenectomy. Consequently, urinary excretion of uroporphyrin I and coproporphyrin I is reduced.