Protoporphyria is a genetic disorder of porphyrin metabolism in which a deficiency of ferrochelatase activity causes excessive accumulation and excretion of protoporphyrin (1,2). Protoporphyrin is excreted in bile, and its deposition in the liver impairs hepatic structure and function (3,4). As a consequence, some patients develop progressive liver damage leading to liver failure (5,6), and may have a rapid downhill course once jaundice develops. Liver transplantation has been necessary when this occurs (7,8). A means by which to stabilize liver function during the waiting period for liver transplantation is needed.
As liver disease in protoporphyria appears to be caused by a toxic effect of protoporphyrin, therapy should be directed to diminish the amount of protoporphyrin to which the liver is exposed. The administration of hematin (ferriheme hydroxide) is of potential benefit because it decreases the production of porphyrins and porphyrin precursors in other porphyrias, including those in which the bone marrow is the predominant site of overproduction (9-13). Heme therapy may also reconstitute hemoproteins in the liver and improve hepatic function (14-16).
In a previous report, hematin was administered to two adult patients with advanced protoporphyric liver disease (17). In both patients blood protoporphyrin levels decreased and liver chemistries improved. We therefore administered hematin to three children with protoporphyric liver disease to determine whether it would stabilize their clinical courses.
This white male patient was diagnosed with protoporphyria at the age of 5 years. Percutaneous liver biopsy at age 12 years demonstrated cirrhosis with birefringent pigment deposits characteristic of protoporphyric liver disease (5). During the following year he deteriorated and underwent orthotopic liver transplantation. At transplantation, his hemoglobin was 12.2 g/dL, total serum bilirubin 8.5 mg/dL (normal <1.3), serum aspartate aminotransferase (AST) 659 U/L (normal <50), serum alanine aminotransferase (ALT) 696 U/L (normal <50), prothrombin time 14.2 seconds (normal 11 to 13.5), erythrocyte protoporphyrin 7,679 mcg/dL (normal 20 to 65), and serum protoporphyrin 448 mcg/dL (normal 0). The liver porphyrin concentration was 5,226 mcg/g wet weight (normal <1.0).
The patient's postoperative course included paralysis, which required 3½ months of ventilator support. This began during the first postoperative week and followed an episode of hemolysis in which the serum protoporphyrin level increased markedly to 1,238 mcg/dL. Serum and urinary levels of delta-aminolevulinic acid (5 mcg/dL and 3 mg/g creatinine) and porphobilinogen (0 mcg/dL and 3.3 mg/g creatinine) were normal. The urinary excretion of uroporphyrin was 83 mcg/day (normal <50) and of coproporphyrin 158 mcg/d (normal <280). A course of thrice weekly plasmapheresis (1.5 volume plasma exchange), followed on each occasion by the intravenous administration of hematin (Panhematin from Abbott Laboratories, Chicago, IL) in a dosage of 3 mg/kg body weight over a 15- to 30-minute interval, was given during this period. This was associated with an improvement in his liver chemistries and a decrease in his blood protoporphyrin levels (Fig. 1). The paralysis resolved, but he was left with a bilateral foot drop.
Ten months after the transplant the patient was admitted with biliary obstruction caused by a stone in his common bile duct. This was managed by ERCP with sphincterotomy and removal of the stone. Afterwards there was a progressive increase in his blood porphyrin levels (see Fig. 1). Chenodeoxycholic acid (12 mg/kg daily) was given for 1 year without a significant effect on his blood protoporphyrin levels (18). Percutaneous liver biopsy obtained 34 months after the transplant showed portal fibrosis with bile ductular proliferation, cholestasis, and the presence of birefringent pigment deposits. There was no evidence of rejection. The porphyrin level in the liver tissue was 1,340 mcg/g wet weight.
One month later the patient was hospitalized with severe epigastric pain radiating to his back, nausea, and vomiting. Weight was 49.5 kg. Blood pressure was 122/84, and there was a sinus tachycardia of 115/beats/min. He had an enlarged, tender liver. Neurologic examination was normal except for the bilateral foot drop. The hemoglobin was 11.8 g/dL, total serum bilirubin 3.8 mg/dL, serum ALT 191 U/L, prothrombin time 13.8 seconds, erythrocyte protoporphyrin 9,466 mcg/dL, and serum protoporphyrin 308 mcg/dL. Viral serologies were negative and serum lipase was normal. Ultrasonography and magnetic resonance imaging (MRI) showed hepatosplenomegaly, but there were no focal defects in the liver or bile duct abnormalities, and the portal vein was patent. ERCP showed a widely patent papillotomy with spontaneous drainage of the bile and a patent biliary system. A minimal stricture was present at the site of anastomosis. The stomach and duodenum appeared normal. The patient was felt to be suffering from a protoporphyric crisis (19,20). Because of the response he had to plasmapheresis and hematin administration previously, he underwent plasma volume exchange (1.5 volumes) followed each time by hematin administration in a dosage of 3 to 4 mg/kg over 15 to 30 minutes, on 11 separate days over a 2-week period. On this regimen he had significant clinical improvement, with resolution of the pain and nausea. His liver chemistries improved, and the erythrocyte protoporphyrin and serum protoporphyrin levels decreased.
He was discharged to continue on the plasma-pheresis and hematin infusions three times weekly and did well except for a decrease in his hemoglobin level that necessitated transfusion with one unit of red cells on four occasions. After 3 months the total serum bilirubin was 0.3 mg/dL, serum ALT 27 U/L, erythrocyte protoporphyrin 3,290 mcg/dL, serum protoporphyrin 19 mcg/dL, prothrombin time 12.4 seconds, and serum creatinine 0.9 mg/dL. Liver biopsy demonstrated less cholestasis and the protoporphyrin level had decreased to 504 mcg/g wet weight.
The regimen of plasmapheresis and hematin infusions was discontinued when he suffered two episodes of gram-negative septicemia. His liver chemistries and blood protoporphyrin levels subsequently worsened, and he had progressive enlargement of his liver and spleen. Ascites and varices developed, and he was listed for retransplantation. Another episode of crisis developed 4½ years after transplantation, and the regimen of plasmapheresis and hematin infusions was reinstated, but he died from a combination of hepatic failure, renal failure, and respiratory compromise.
This white female patient was diagnosed with protoporphyria at age 4 years. Hepatomegaly and abnormal liver chemistries were noted at age 14 years. Erythrocyte and serum protoporphyrin levels were 2,450 mcg/dL and 95 mcg/dL, respectively. A percutaneous liver biopsy specimen demonstrated fibrosis expanding the portal tracts, with probable early cirrhosis. Bile ductular proliferation was present, and the canaliculi and Kupffer cells contained dark brown pigment that was birefringent when examined by polarization microscopy. She was subsequently referred for evaluation for liver transplantation.
While the evaluation was proceeding, the patient developed severe abdominal and back pain accompanied by constipation and vomiting. She was hospitalized and found to have a sinus tachycardia of 124 beats/min and a blood pressure of 152/90. Jaundice was present and the liver and spleen were enlarged. Laboratory evaluation demonstrated an increase in the serum bilirubin level to 3.9 mg/dL from 1.5. The serum ALT level had increased to 155 U/L and the AST to 361 U/L, compared with her usual range of 100-150. The prothrombin time had risen to 14.4 seconds. The erythrocyte protoporphyrin level was 2,780 mcg/dL and the serum protoporphyrin level was 239 mcg/dL. A screening test for excess urine porphyrins was negative. The hemoglobin level was 9.7 gm/dL and the white blood count 6,900 with a normal differential. Serum amylase and lipase levels were normal. Liver and renal ultrasound revealed hepatosplenomegaly, but no focal hepatic defects, biliary dilatation, or hydronephrosis. Cultures were negative.
The patient was initially treated with intravenous hydration, ranitidine, meperidine, and promethazine for 5 days without improvement. She was felt to be experiencing a crisis and was started on hematin (3 mg/kg), administered over a 15- to 30-minute interval on 5 consecutive days. She began to improve clinically following the second dose. Her blood pressure decreased to a level of 105/56 and her pulse decreased to 97 beats/min. Her abdominal pain and nausea resolved. The bilirubin level fell to 1.3 mg/dL, and the ALT and AST levels decreased to 81 and 129 U/L, respectively. The prothrombin time remained stable at 15 seconds. Porphyrin determinations obtained 3 weeks later showed that the erythrocyte protoporphyrin level had decreased to 1,610 mcg/dL and the serum protoporphyrin to 1.5 mcg/dL. The patient subsequently remained stable and underwent successful liver transplantation 3 months later. At the time of her most recent follow-up (4 months after transplantation) she was doing well, with erythrocyte and serum protoporphyrin levels of 1,710 mcg/dL and 29 mcg/dL.
This white male patient had photosensitivity since infancy. At age 10½ years he was noted to have abnormal liver chemistries. Examination demonstrated lichenified skin lesions on the dorsum of his hands and on the face. The liver was percussed over a span of 11.5 cm and was palpable 7 cm below the costal margin. The spleen was also palpable. Laboratory data showed the total serum bilirubin to be 0.7 mg/dL with a direct reacting fraction of 0.3, the serum ALT 204 U/L, and the serum AST 145 U/L. Coagulation parameters were normal. The erythrocyte protoporphyrin and serum protoporphyrin levels were 2,307 mcg/dL and 24 mcg/dL, respectively. Evaluation for viral hepatitis and other metabolic liver disorders was negative. A diagnosis of protoporphyria with liver involvement was made. Cholestyramine (12 to 24 g daily) was given for several weeks without improvement (21). Percutaneous liver biopsy was done and demonstrated bridging portal fibrosis and nodular formation indicating early cirrhosis. There was an accumulation of dark brown pigment in bile ducts, canaliculi, and Kupffer cells, which was birefringent under polarizing microscopy. The porphyrin concentration in the liver tissue was 350 mcg/g wet weight.
Hematin therapy (3 mg/kg) was administered over a 15-to 30-minute interval three times weekly. The serum transaminase levels decreased within 4 weeks and the hepatosplenomegaly resolved, although there was no change in his erythrocyte protoporphyrin (range 2,173 to 3,258 mcg/dL) or serum protoporphyrin (range 5 to 40 mcg/dL) levels. Following discontinuation of the hematin therapy on two occasions there was a significant rise in his transaminase levels within 4 weeks. After resuming therapy the levels normalized. A liver biopsy obtained 16 months after the first biopsy demonstrated pigment deposition with bridging fibrosis, not significantly changed from the first biopsy, and the porphyrin level was 650 mcg/g wet weight. The erythrocyte protoporphyrin level was 2,512 mcg/dL and the serum protoporphyrin level 29 mcg/dL. Hematin was withdrawn on a third occasion, again resulting in a worsening of liver chemistries within 4 weeks, which included direct hyperbilirubinemia. Therapy was again resumed three times weekly. The coagulation parameters and renal function remained normal throughout therapy.
From age 13 to 14½ years the patient had a growth spurt accompanied by progressive hepatosplenomegaly. The liver was greater than 20 cm in span. this occurred in the face of continued hematin therapy, which required upward adjustment because of the weight gain. The urinary excretion of uroporphyrin and coproporphyrin was 52 mcg/day and 161 mcg/day, respectively. Because of the progressive hepatosplenomegaly, the patient was placed on the list for liver transplantation. His total serum bilirubin rose to 4.7 mg/dL, serum ALT 100 U/L, serum AST 348 U/L, prothrombin time 16.8 seconds, erythrocyte protoporphyrin 6,910 mcg/dL, and serum protoporphyrin 215 mcg/dL. He subsequently underwent successful liver transplantation, and at the time of most recent follow-up (1 month after transplantation) was doing well.
Erythrocyte and serum protoporphyrin levels were measured fluorometrically after solvent partitioning (4,8). Liver porphyrin content was determined fluorometrically after extracting the tissue with 0.6 N perchloric acid/methanol (1:1, vol/vol) (4,8). Other measurements were done by clinical chemistry laboratories.
The three children with protoporphyric liver disease described here had a beneficial response to hematin therapy. Patients 1 and 2 were given hematin while experiencing crises that were characterized by the worsening of liver chemistries and blood protoporphyrin levels, accompanied by severe abdominal or back pain and neurologic dysfunction (19,20). Both had relief of their symptoms, with improvement in both liver chemistries and blood protoporphyrin levels. In patient 1, plasmapheresis may have contributed to the improvement, but this was not used in the second patient. Transfusion therapy along with blood exchange has also been used in the management of this condition (20).
The rationale for using hematin therapy in patients with acute porphyric attacks (9-11) is that hematin suppresses hepatic delta-aminolevulinic acid synthase activity, which is the rate-limiting step in hepatic heme formation. This diminishes the production of porphyrin precursors, which may be neurotoxic. In experimental animals 50% to 70% of administered hematin is taken up by the liver (22). Studies in patients with congenital erythropoietic porphyria indicate that a portion of the hematin that is not removed by the liver is taken up by bone marrow cells, suppressing the overproduction of porphyrins that occurs in these cells (12,13). Presumably, this also happens in protoporphyria, resulting in decreased protoporphyrin formation.
However, the rapid improvement in liver chemistries in the three cases was not well explained by the effect of hematin therapy on protoporphyrin formation alone. Rather, it suggests that hematin therapy enhances hepatic function. There is both experimental and clinical evidence that exogenously administered heme reconstitutes hepatic cytochromes P450 by combining with apo-cytochromes (14-16,23). There is also evidence that other hepatic apoproteins that require heme as a prosthetic group are similarly reconstituted (15).
Hematin therapy may have complications. The most serious is renal injury, but that has occurred only at a high dose (12 mg/kg body weight) (24). A coagulopathy develops, which is caused by a breakdown product of hematin (25), and the compound should be given quickly after it is dissolved in aqueous solution. Thrombophlebitis also occurs and necessitates that hematin be administered through a freely flowing intravenous line, requiring a central venous catheter in children for repeated infusions. These complications may be reduced by using heme arginate, a derivative of heme that is presently undergoing clinical trials in the United States and is already available in Europe, or by complexing heme to human serum albumin prior to intravenous infusion (15).
Hematin therapy in patients 1 and 3 stabilized hepatic function over a period of several months. This indicates that the rapid downhill course that has been observed in patients with protoporphyric liver disease who develop jaundice can be interrupted and allow time for a donor to be identified for liver transplantation. Hematin therapy does not appear to reverse advanced liver disease in these patients, and they deteriorate when therapy is stopped. However, if the liver disease is identified at an early stage they might be stabilized so that liver transplantation can be avoided for a prolonged period. Hematin therapy had been used in some patients with hepatic porphyrias for several years without adverse side effects. There is the potential problem of iron overload with repeated infusions, but the amount of iron delivered with each 100 mg of hematin is only 8.1 mg. Indeed, there was no histologic evidence of iron overload in the liver biopsy of patient 3, who received hematin over a prolonged period.
In summary, the use of hematin therapy in children with protoporphyric liver disease appears to be beneficial, particularly in those who experience acute crises. Based on the results of the present study, we recommend giving patients with liver damage, as documented by liver chemistries and typical biopsy features (5,6), a trial of hematin in a dosage of 3 to 4 mg/kg administered over 15 to 30 minutes three times weekly. For patients experiencing a crisis or being stabilized while awaiting liver transplantation, daily administration should be used. If there is not a satisfactory response, plasmapheresis should be added to the regimen, with a 1.5 volume exchange before hematin is administered.
Acknowledgment: These studies were supported by Research Grant DK 26466 from the National Institutes of Health, the Cecil J. Watson Laboratory Endowment Fund, and the Adrian Bennett Memorial Fund.
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