—  SPECIALTY CONFERENCE  —

Liver Pathology

Case 4 - Sickle Cell Anemia

Julia Iezzoni
University of Virginia
Charlottesville, VA





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Clinical History
The patient, a 42-year-old African-American male, underwent a cholecystectomy for cholelithiasis. During the surgical procedure, a liver biopsy was performed. [Figure 4-1 (H&E, 200X), Figures 4-2, 4-3, 4-4 (H&E, 400X), Figure 4-5 (Trichrome, 200X), Figure 4-6 (Prussian blue, 200X).


Case 4 - Figure 1 - Sections of the liver biopsy show the characteristic sickled hepatocytes within congested and dilated sinusoids. (H&E, 200X and 400X, respectively)
Case 4 - Figure 2 - Sections of the liver biopsy show the characteristic sickled hepatocytes within congested and dilated sinusoids. (H&E, 200X and 400X, respectively)
Case 4 - Figure 3 - Erythrophagocytosis by Kupffer cells is identified. (H&E, 400X)

Case 4 - Figure 4 - Extramedullary hematopoesis is seen. (H&E, 400X)
Case 4 - Figure 5 - Trichrome stain demonstrates perivenular fibrosis. (Trichrome, 200X)
Case 4 - Figure 6 - Markedly increased iron stores are identified. (Prussian blue 200X)


Diagnosis:
Sickle cell anemia

Pathologic Findings:
Sections of the liver biopsy show the characteristic sickled erythrocytes within congested and dilated sinusoids. Kupffer cell hyperplasia and focal extramedullary hematopoesis are identified. A trichrome stain demonstrates perivenular fibrosis. Markedly increased (4+) iron stores are identified on the Prussian blue stain, with the iron present in both hepatocytes and Kupffer cells and distributed throughout all zones of the hepatic lobules.

Discussion

Background
Hemoglobin, which transports oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs, is composed of a tetramer of globin chains. The normal adult form of hemoglobin consists of a pair of a chains (141 amino acids long) and a pair of b chains (146 amino acids long). Accordingly, the major normal adult hemoglobin (HbA) has the structure a2b2. The conformation of the globin chains changes reversibly depending on the state of oxygenation.

Hemoglobinopathies are disorders that affect the structure, function, or production of hemoglobin, and there are five major classes of hemoglobinopathies: structural hemoglobinopathies; thalassemias; thalassemic hemoglobin variants; hereditary persistence of fetal hemoglobin; and acquired hemoglobinopathies [1]. Sickle cell diseases, which are a type of structural hemoglobinopathy, are disorders in which the erythrocytes undergo sickling when they are deoxygenated and thereby produce prominent clinical manifestations [2]. These diseases are caused by a mutation that changes the amino acid sequence of a globin chain, and this in turn, alters the physiologic properties of the variant hemoglobins. In the case of sickle cell hemoglobin (HbS), a mutation in the b-globin gene changes the sixth amino acid from glutamic acid to valine (a2 b26 Glu ŪVal). Sickle cell anemia, the prototype sickle cell disease, is the homozygous state for the sickle cell gene (HbSS). This discussion will focus on the sickle cell anemia.

Hemoglobin S occurs with greatest prevalence in tropical Africa, where the heterozygote frequency ranges between 20%-40% of the population depending on the specific geographic area. It is also relatively common in the United States; HbS occurs in heterozygous form in approximately 8% of African-Americans and in homozygous form in 1 in 400 of this population.

Due to the alteration in primary structure, molecules of HbS have a strong tendency to polymerize reversibly into microtubules when deoxygenated [1]. These aggregates of microtubules stiffen the cytoplasmic membrane and increase the cytoplasmic viscosity of the affected erythrocytes, resulting in the characteristic sickle shape. Importantly, because of these changes, the sickled cells loose the pliability needed to transverse capillaries. In addition, repetitive cycles of sickling and unsickling results in severe injury to the cytoplasmic membrane of the affected erythrocytes; due to this membrane injury, these "irreversibly" sickled erythrocytes are abnormally adherent to the endothelium [3]. This feature, in conjunction with the decreased cellular pliability, as well the complex interplay of a variety of non-erythrocyte-related factors, results in repeated episodes of vaso-oclusion, as the rigid, adherent sickled erythrocytes occlude and clog capillaries and small venules [3]. This vaso-occlusion, in turn, results in tissue ischemia and microinfarctions.

The clinical manifestations of sickle cell anemia are vast and are beyond the scope of this discussion. In sum, they are dominated by lifelong hemolytic anemia, sequelae of repeated of vaso-occlusive events in a wide variety of organs and tissues (which often results in pain and ischemic type tissue damage), and increased susceptibility to infections, particularly S. pneumoniae, which in part is related to absent splenic function (that is often due to autosplenectomy). Typically patients achieve a steady state of relative well being that is periodically interrupted by a crisis, which may be of a vaso-occlusive, aplastic, sequestration, or hemolytic type. The disease is readily suspected on the basis of the clinical features in conjunction with the characteristic erythrocyte morphology on a peripheral blood smear. The diagnosis is confirmed by hemoglobin electrophoresis along with an assay for hemoglobin sickling, solubility, or oxygen affinity, such as the sickle solubility test. The diagnosis is usually established in childhood, but occasional patients, often compound heterozygous states, do not develop symptoms until the onset of puberty, pregnancy, or adult life [1].

Hepatobiliary Manifestations of Sickle Cell Anemia
Liver and biliary tract dysfunction are common complications of sickle cell disease and result in a variety of clinicopathologic syndromes, as described below. In sickle cell anemia patients, the typical clinical setting in which a liver biopsy is performed is during cholecystectomy, though occasionally a biopsy is performed for evaluation of hepatomegaly and/or liver test abnormalities [4].

Characteristic Morphologic Features in the Liver
In sickle cell anemia, morphological changes in the liver are common, and they are unrelated to as whether or not the patient is having a sickling crisis at the time of the biopsy [4, 5, 6, 7, 8, 9]. The morphologic features are a direct result of the pathophysiologic consequences of the disease. The relatively anoxic environment of the hepatic sinusoids results in intrahepatic erythrocyte sickling. Accordingly, aggregates of sickled erythrocyte are particularly prominent within the perivenular zone, producing sinusoidal dilatation and congestion, which may be panlobular, or on occasion, results in peliosis. The finding of dilated sinusoids congested with sickled erythrocytes is the "hallmark" morphologic feature of sickle cell disease in the liver. Futhermore, the aggregates of packed sickle cells may cause vaso-occlusion, which in turn, may cause local ischemic necrosis. This may result in fibrosis and possibly eventual cirrhosis (see below).

Other characteristic morphologic features include Kupffer cell hyperplasia and erythrophagocytosis by Kupffer cells. This latter feature may be particularly evident in patients without a spleen (either due to elective splenectomy or autosplenectomy), in which case the liver then serves as the major site of erythrocyte destruction. Also, hemosiderosis often is present, and the extent is a function of the number of transfusions that the patient has received. The increased iron stores are within both hepatocytes and Kupffer cells and are distributed throughout all lobular zones. Other morphologic features may include perivenular fibrosis, extramedullary hematopoesis, and foci of hepatocyte necrosis randomly distributed throughout the lobule.

Both portal and lobular inflammation, predominantly lymphocytic, may be seen in the setting of sickle cell anemia. From the published literature, however, it is difficult to determine whether this inflammation is due solely to the disease. These patients are at risk for transfusion-acquired viral hepatitis, and the reported series were either prior to or include at least some cases prior to available testing for hepatitis C (and in some instances, hepatitis B). From a practical perspective, if hepatitic features are present and well developed, the possibility of a co-existent hepatitis, such as hepatitis C or autoimmune hepatitis, merits consideration.

Liver Chemistries
Sickle cell anemia is characterized by increased total bilirubin, which may be either predominantly of the conjugated (direct) or unconjugated (indirect) type. This increase in bilirubin is present not only in symptomatic patients but also in those patients with steady state disease who are asymptomatic in regard to the liver [4]. In addition, in steady-state disease, typically there is only minimal to mild elevation of transaminases [10]. More markedly elevated transaminases merits investigation of other possible etiologies of liver disease, such as a co-existent viral hepatitis. Alkaline phosphastase also may be mildly to moderately elevated, but higher elevations may be due to biliary tract obstruction (secondary to choledocholithiasis, which is relatively common in this patient population, as described below) or a vaso-oclusive crisis involving the bones rather than pathology of the liver.

Development of Cirrhosis
In patients with sickle cell anemia, it is difficult to precisely determine the incidence of cirrhosis that is due solely to this disease, as these patients are at risk for transfusion-acquired viral hepatitis. In some series, cirrhosis has been observed in up to 16% to 29% of patients with sickle cell disease [11]. However, most of these studies were performed before the availability of sensitive tests for hepatitis B and hepatitis C; as such, co-existent viral hepatitis cannot be excluded as a contributory factor for the development of cirrhosis in these cases. Within this limitation, however, it does appear that in some cases, sickle cell anemia alone may result in progressive fibrosis and cirrhosis. In this setting, both repeated episodes of microinfarctions as well as hepatic iron overload have been proposed as major causative factors of the chronic liver injury and cirrhosis.

Acute Hepatic Failure in Sickle Cell Disease
Acute hepatic failure is an uncommon, though in some cases, catastrophic, complication of sickle cell anemia [12, 13, 14, 15]. Also known as sickle cell intrahepatic cholestasis or sickle cell hepatopathy, it is characterized by sudden onset of right upper quadrant pain, progressive tender hepatomegaly, extreme hyperbilirubinemia, in some cases significantly increased transaminases, and variable degrees of hepatic dysfunction, such as prolonged prothrombin time. The few reports of the liver pathology in this setting note the characteristic hepatic morphologic features of sickle cell anemia (as described above) as well as marked cholestasis, hepatocyte ballooning, and in some cases, centrilobular necrosis. The clinical outcome is variable, and the condition often is fatal.

Other Hepatic Syndromes and Lesions
Acute hepatic crisis is one of the most common acute hepatic complications of sickle cell anemia [15]. It is characterized by right upper quadrant pain, increasing jaundice, hepatomegaly, mild to moderate elevation of transaminases, and elevations in bilirubin that seldom exceeds 15 mg/dl (257 mmol/l). It has a short, self-limited clinical course and typically does not come to liver biopsy.

Hepatic sequestration also may occur in sickle cell anemia, though it is uncommon [15]. It is results from the massive sequestration of red blood cells in the liver and presents as acute hepatic enlargement associated with rapidly falling hemoglobin. Typically, a liver biopsy is not performed.

In patients with sickle cell anemia, hepatic infarction may occur rarely, and it is usually caused by hepatic artery rather than portal vein occlusion [12, 16]. There is also an increased incidence of liver abscesses in patients with sickle cell anemia [16]; in some cases, this may be due to secondary infection of hepatic infarcts. Focal nodular hyperplasia, possibly related to local ischemia from sickle cell thrombosis, has been reported in children sickle cell anemia [17, 18]. In addition, nodule regenerative hyperplasia of the liver has been reported in an adult with sickle cell disease [19]. Sickle cell thrombosis, with subsequent local ischemia, is proposed as the pathologic mechanism in this setting, as well.

Cholelithiasis in Sickle Cell Disease
There is high incidence of gallstones in patients with sickle cell disease, though the exact incidence varies between studies [11, 12, 16]. As in other hemolytic states, the gallstones in sickle cell disease are typically of the pigmented (calcium bilirubinate) type and result from increased bilirubin excretion. Children under 10 years are reported to have a 14% incidence of cholelithiasis, and gallstones have been found in children as young as 6 years. The incidence increases with patient age, and approximately 50% to 70% of adult patients have choleliathisis. Studies vary as to whether or not this incidence is higher in women than men. Choledocholithiasis also is common in adult patients with sickle cell anemia, with a reported incidence of 14%. The increased incidence of choledocholithiasis in sickle cell anemia predisposes this patient population to biliary tract obstruction and its associated sequelae. Therefore, hyperbilirubinemia in patients with sickle cell anemia may be due not only to hemolysis or intrahepatic causes but also to extrahepatic etiologies such as choledocholithiasis. Ultrasound of the biliary tract is highly accurate in the evaluation for the latter possibility [16].

Differential Diagnosis
The morphologic findings in the liver biopsy typically can be readily attributed to sickle cell anemia when the complete clinical history is provided and/or the characteristic sickled erythrocytes are identified within the hepatic sinusoids. The diagnosis may become more challenging in the absence of the complete history or when the sickled erythrocytes are overlooked in the biopsy specimen. As such, it is useful to include a brief evaluation of erythrocyte morphology in the routine review of all liver biopsies specimens.

If the complete clinical history is not provided or the presence of sickled erythrocytes is overlooked, the presence of sinusoidal congestion and dilatation raises of differential diagnosis of entities characterized by this feature [20]. In addition, the hepatic hemosiderosis raises the differential diagnoses of entities in which increased hepatic iron stores dominate the histologic findings.

References:
  1. Edward J Benz: Hemoglobinopathies. In Harrison's Principles of Internal Medicine (16th ed). D Kasper, AS Fauci, DL Longo, E Braunwald, SL Hauser, JL Jameson (eds). New York, McGraw-Hill, 2005; pp 593-601.

  2. Beutler E: Disorders of hemoglobin structure: sickle cell anemia and related abnormalities. In Williams Hematology (7th ed). MA Lichtman, TJ Kipps, K Kaushansky, E Beutler, U Seligsohn, JT Prchal (eds). New York, McGraw-Hill, 2006; pp 667-683.

  3. Chiang EY, Frenette PS. Sickle cell vaso-occlusion. Hematol Oncol Clin N Am 19:771-784, 2005.

  4. Charlotte F, Bachir D, Nenert M, Manier P, Galacteros F, Dhumeaux, Zafrani S. Vascular lesions of the liver in sickle cell disease. Arch Pathol Lab Med 119:46-52, 1995.

  5. Rosenblate HJ, Eisenstein R, Holmes AW. The liver in sickle cell anemia. A clinico-pathologic study. Arch Path 90:235-245, 1970.

  6. Bauer TW, Moore GW, Hutchins GM. The liver in sickle cell disease. A clincopathologic study of 70 patients. Am J Med 69:83-837, 1980.

  7. Omata M, Johnson CS, Tong M, Tatter D. Pathologic spectrum of liver disease in sickle cell disease. Digest Dis Sci 31:247-256, 1986.

  8. Mills LR, Mwakyusa D, Milner PF. Histopathologic features of liver biopsy specimen in sickle cell disease. Arch Pathol Lab Med 112:290-294.

  9. Teixeira AL, Viana MB, Roquete MLV, Toppa NH. Sickle cell disease: A clinical and histopathologic study of the liver in living children. J Ped Hematol/Oncol 24:125-129, 2002.

  10. Kotila T, Adedapo K, Adedapo A, Oluwasola O, Fakunle E, Brown B. Liver dysfunction in steady state sickle cell disease. Annals Hepatol 4:261-263, 2005.

  11. Edwards CQ. Anemia and the liver. Hepatobiliary manifestation of anemia. Clin Liver Dis 6:8891-907, 2002.

  12. Schubert TT. Hepatobiliary system in sickle cell disease. Gastroenterol 90:2013-2021, 1986.

  13. Ahn H, Li C-S, Wang W. Sickle cell hepatopathy; Clinical presentation, treatment, and outcome in pediatric and adult patients. Pediatr Blood Cancer 45:184-190, 2005.

  14. Irizarry K, Rossbach HC, Ignacia JRA, Winesett MP, Kaiser GC, Kumar M. Sickle cell intrahepatic cholestasis with cholelithiasis. Ped Hemat Oncol 23:95-102, 2006.

  15. Ahmed S, Shahid RK, Russ LA. Unusual causes of abdominal pain: sickle cell anemia. Best Prac Res Clin Gastroenterol 19:297-310, 2005.

  16. Rao VM, Mapp EM, Weschler J. Radiology of the gastrointestinal tract in sickle cell anemia. Sem Roentgenol 22:195-204, 1987.

  17. Markowitz RI, Harcke HT, Ritchie WGM, Huff DS. Focal nodular hyperplasia of the liver in a child with sickle cell anemia. Am J Radiology 134:594-7, 1980.

  18. Heaton ND, Pain J, Cowan NC, Salisbury J, Howard ER. Focal nodular hyperplasia of the liver: a link with sickle cell disease? Arch Disease Childhood 66:1073-1074, 1991.

  19. Al-Mukhaizeem KA, Lamoureux E, Rosenberg A, Sherker AH. Nodular regenerative hyperplasia and focal global glomerulosclerosis associated with sickle cell anemia. Dig Dis Science 47:443-447, 2002.

  20. Kakar Sanjay, Kamath PS, Burgart LJ. Sinusoidal dilatation and congestion in liver bipsy. Is it always due to venous outflow impairment? Arch Pathol Lab Med 128:901-904, 2004.