Laboratory findings. Mild microcytic hypochromic anemia occurs in 20-30% of patients. The bone marrow demonstrates a variable percentage of erythropoietic precursor with red fluorescence. The marrow morphology is otherwise normal. The disorder results from a deficiency of the ferrochelatase activity causing protoporphyrin to accumulate in excessive levels in erythrocytes, bile, and feces but not urine. Increased erythrocyte protoporphyrin confirms the diagnosis. In comparison to iron deficiency and lead poisoning, the increase erythrocyte protoporphyrin is free and chelated to zinc. Light exposed skin biopsies may have an amorphous material staining positive for periodic acid Schiff is found in and around capillary walls. This finding is not specific to protoporphyria and has been reported in variegate porphyria and porphyria cutanea tarda. Liver biopsy specimens show portal inflammation and fibrosis along with the deposition of a brown pigment. In 10% of patients severe liver disease develops and the livers appear black and cirrhotic. When examined by polarization microscopy the pigment deposits are birefringent and by electron microscopy demonstrate crystals. The crystals are composed of protoporphyrin.
Treatment. To increase tolerance to light oral administration of beta carotene may be useful, but may not occur until 1-3 months after initiation of therapy. The only known side affect appears to be the yellow discoloration to the skin. To reverse hepatic protoporphyrin accumulation red blood cell transfusion and I.V. hematin administration may be tried which suppress excess protoporphyrin production. AN alternative is oral administration of cholestyramine or activated charcoal to interrupt the intrahepatic circulation of protoporphyrin. With the exception of liver disease development the manifestations of the disease have a favorable prognosis and patients live a normal lifespan.
