High levels of urinary porphyrins in the urine are due to porphyria. Porphyria is a disorder of porphyrin metabolism characterized by increased excretion of porphyrins and porphyrin precursors in the urine and feces. Porphyria is a congenital disorder caused primarily by deficiencies in various enzymes related to heme synthesis, and there is a family history of the disease. What causes protoporphyria? I. Causes 1. Protoporphyria disorders of porphyrin metabolism occur in young red blood cells and hepatocytes in bone marrow bone marrow, liver, blood reticulocytes and fibroblasts lack of iron chelatase (the last enzyme in the heme biosynthesis process), thus leading to protoporphyrin accumulation, and the activity of this enzyme in patients is only 10% to 20% of normal. 2, the disease is an autosomal dominant disease with varying degrees of expression or incomplete epiphenomenon. Most gene carriers do not show symptoms, so families can often find people who do not have clinical symptoms, but have mild biochemical abnormalities in their red blood cells, plasma and feces. 3. The biochemical defects due to genetic factors make the protoporphyrin and the globulin of the red blood cells poorly bound, and the free protoporphyrin enters the plasma from the red blood cells and the liver, where it binds to albumin and hemoglobin. When the protoporphyrin molecule gradually returns to its original state, the absorbed light energy fluoresces and forms free chemical groups and peroxides. The disease is autosomal dominant, and the ferrous chelatase gene on chromosome 18q21.3 is defective, resulting in the lack of ferrous chelatase required to catalyze the synthesis of protoporphyrin IX and ferrous ions into heme, leading to excessive accumulation of protoporphyrin IX in the body. Free protoporphyrin enters the bloodstream from red blood cells and liver and is deposited in the endothelial cells of skin capillaries, causing skin photosensitivity reactions. However, protoporphyrin IX is poorly water-soluble and strongly lipid-soluble, and has poor affinity for skin, bone, teeth, and other tissues, resulting in mild skin damage and no protoporphyrin deposition in bone and teeth. Although most patients with the gene defect have abnormal porphyrin metabolism, they have no clinical symptoms, and paternal inheritance is rare. Thus, it is assumed that there is more than one allele that determines the clinical manifestations of the disease. In addition, metabolic abnormalities are more common in males than females, and the cause is unknown. Protoporphyrin is mainly excreted from the feces via the biliary tract, and liver damage due to this disease is caused by deposition of protoporphyrin in the liver tissue. The liver removes large amounts of protoporphyrin from the plasma, and when the liver secretes large amounts of protoporphyrin, it can block the capillary bile ducts and cause bile stasis. Restricted excretion of protoporphyrin from capillary epithelial cells can lead to accumulation of protoporphyrin in hepatocytes, and biliary sludge interferes with intracellular oxidative phosphorylation reactions, leading to cell death and liver tissue fibrosis.