Entecavir-associated thrombocytopenia

Abstract

Entecavir (ETV) is widely used in the treatment of hepatitis B, but there are only a few reports about entecavir-associated thrombocytopenia, and it is considered as an immediate response and inappropriate to continue the treatment with other nucleoside analogues. Now, we report the third case, and this case was delayed response and we switched to treatment with tenofovir (TDF). There was a 66-year-old female who was infected with hepatitis B virus (HBV). Her platelet count decreased from 111*10⁹/L to 3*10⁹/L and was prone to gum bleeding and skin ecchymosis after she received ETV treatment for 88 days. As a treatment option, ETV was replaced by TDF immediately, frequent platelets transfusions and thrombopoietin were applied for several days, daily prednisone of 50 mg was concomitantly taken, and then platelet count improved after 10 days. She was diagnosed with entecavir-associated thrombocytopenia after analysis of the temporal relationship and exclusion of other causes of thrombocytopenia by blood and bone marrow examinations. Our case suggested that the platelet count should be monitored regularly in patients during ETV treatment, and it may be a feasible option to choose TDF to maintain antiviral treatment when entecavir-associated thrombocytopenia occurs.

Introduction

Many people infected with hepatitis B virus (HBV) and for the development of chronic hepatitis B (CHB), hepatitis Bassociated liver cirrhosis (HBV-LC) or hepatocellular carcinoma (HBV-HCC) in China. ¹ The only effective method to block the progression is antiviral therapy, and entecavir (ETV) is a first-line drug for the treatment of chronic HBV infection, which has been used for decades and proven to have slight side effects and good tolerance. In rare cases, ETV would be associated with severe thrombocytopenia, there are two case reports of entecavir-associated thrombocytopenia, and it is considered as an immediate response and inappropriate to continue the treatment with nucleoside analogues.^2,3 Here, we report the third case of a female who developed severe thrombocytopenia with bleeding after she had received entecavir for 88 days, and switched to treatment with tenofovir.

Case presentation

A 66-year-old female was diagnosed with CHB in Nanjing Jiangbei Hospital on 17 September 2019. Diagnosis results on hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and hepatitis B core antibody (anti-HBc) were positive, while antibodies to hepatitis A, hepatitis C, hepatitis D, and hepatitis E were negative. There was no evidence of infection with cytomegalovirus, HIV virus, herpes simplex virus, or Epstein–Barr virus. In addition, the results were also negative for serologic markers of autoimmune diseases (antinuclear antibody (ANA), antinuclear ribonucleoprotein (anti-nRNP), anti-Smith antibody (anti-Sm), anti-Sjogren’s syndrome antigen A antibody (anti-SSA), anti-Ro-52 antibody (RO-52), anti-Sjogren’s syndrome antigen B antibody (anti-SSB), anti-scleroderma-70 antibody (anti-ScL-70), anti-histidyl-transfer RNA synthetase antibody (anti-JO-1), centromere protein B (CB), antidouble-stranded DNA antibody (anti-dsDNA), nucleosome (NUC), histone (HI), anti-ribosomal P-protein antibody (RIB), anti-PM/Scl antibody (PM-Scl), proliferating cell nuclear antigen (PCNA), anti-mitochondrial antibody (AMA), anti-liver and kidney microsomal antibody (LKM), anti-liver cytosol antigen type 1 antibody (LC-1), and soluble liver antigen (SLA) were all negative). Meanwhile, alanine aminotransferase (ALT): 41 IU/L and aspartate aminotransferase (AST): 41 IU/L. HBV-DNA in serum was 6.14  × 10⁶ IU/ml, and the platelet count was 111*10⁹/L. An abdominal magnetic resonance imaging (MRI) scan showed signs of fatty liver. The patient started taking ETV 0.5 mg/day after being diagnosed with CHB. She did not experience any discomfort during the treatment.

Till December 13, she found herself prone to gum bleeding and skin ecchymosis without nasal hemorrhage or sclera bleeding, She denied epistaxis, melena, hematochezia, hematuria, or other bleeding manifestations, and without other chronic or neoplastic disease. Results of blood examination showed that platelet count dropped to 3*10⁹/L, while white blood cell (WBC) and hemoglobin (HGB) remained normal. HBV-DNA in serum was raised to 4.42 E+02 IU/ml with ALT: 52 U/L, AST: 54 U/L, IgA: 2.15 g/L, IgG: 17.90 g/L, and IgM 1.54 g/L. On physical examination, her temperature was 36.9°C; blood pressure, 116/77 mmHg; pulse, 67 beats/min; and respiratory rate, 18 beats/min. She looked tired but had no pallor, icterus, or generalized lymphadenopathy. The anterior nares were clear without epistaxis. The mucous membrane was moist, and the oral mucosa of the oropharynx has many scabs and dried blood. Auscultation of chest revealed that S1 and S2 were normal, without fricative, murmur, gallop, or blister, and the patient had normal breath sounds. Her abdomen was soft without tenderness, hepatosplenomegaly, or ascites. The skin was warm and dry, with several ecchymoses on the chest and back.

She immediately underwent bone marrow aspiration. The bone marrow examination revealed that the hyperplasia was significantly active, granulocytic and erythroid hyperplasia were active, megakaryocytes were common, and platelets were rare. Immunotype lymphocytes occupy about 12% of nucleus cells, and the proportion is reduced. Among them, precursor B-lymphocytes account for 0.5% of lymphocytes, which increases, but there is no obvious light-chain restriction. The cells in the primitive area occupy about 1% of the nuclear cells and are scattered. Monocytes occupy about 4% of the nucleus cells and have a mature phenotype. Granulocytes accounted for about 68% of nuclear cells, and no significant abnormalities were observed (Figure 1(a)). Peripheral blood flow cytometry showed a significant increase in B-lymphocytes (29.20%) (Figure 1(b)). All performance was in accordance with thrombocytopenia.

Figure 1.

Megakaryocyte mature hindrance in bone marrow and the changes of B-lymphocytes in peripheral blood. (A) Megakaryocyte mature hindrance in bone marrow and (B) peripheral blood flow cytometry showed a significant increase in B-lymphocytes.

Platelet count may be decreased by the factor of aplastic anemia, leukemia, cancer, severe infections, immune abnormalities, drugs, vaccines, and so on.^4,5 Since the patient had no history of other medications or infections while taking ETV, and no other causes of thrombocytopenia were identified. The patient was diagnosed with entecavir-associated thrombocytopenia.

ETV medication was replaced by tenofovir (TDF) immediately. Since the patient was in urgent condition, frequent platelets transfusions and thrombopoietin were applied for several days, and daily prednisone of 50 mg was concomitantly taken. Platelet count increased after 10 days, and her symptoms of bleeding faded away gradually. The platelet count reached 297*10⁹/L after 18 days (Figure 2).

Figure 2.

The changes of platelet count after using prednisone of 50 mg daily. The level of platelet count was raised after 10 days with prednisone of 50 mg daily.

Discussion

Thrombocytopenia, characterized by low platelet count and mucocutaneous bleeding, is defined as decreased platelet numbers along with the absence of decreased megakaryocytes in the bone marrow. There are some cases of thrombocytopenia caused by drugs, called drug-induced thrombocytopenia (DITP). The specific mechanism is not recognized, and the etiology is partly due to the direct destruction of platelets by the drugs. The second is that the drug activates autoimmunity and induces the production of drug-dependent antiplatelet antibodies which can bind on glycoprotein Ib-IX, glycoprotein IIb-IIIa, and plateletendothelial cell adhesion molecule-1; all of the above causes eventually lead to thrombocytopenia.^5,6

There are five case reports of nucleoside analogue (NA)-associated thrombocytopenia, and only two with entecavir-associated thrombocytopenia—one had rheumatoid arthritis with decompensated liver cirrhosis, and thrombocytopenia appeared after 4 days of using ETV, and the other was a myeloma patient who had received rituximab, and thrombocytopenia occurred after 5 days of using ETV; both patients were successfully treated by discontinuation of ETV and intravenous immunoglobulin. Summarizing all three patient data, we found that they were all over 60 years old, which prompted the conclusion that this complication may occur more frequently in elderly women. In consideration of the onset time of entecavir-associated thrombocytopenia, we found that two cases had abnormal changes in immune function that happened in 1 week and the last one was significantly delayed—the patient had no underlying disease other than CHB, and therefore, entecavir-related thrombocytopenia was not only an immediate response, but also a delayed response. It was speculated that the occurrence time of entecavir-associated thrombocytopenia may be related to the degree of immune environment imbalance of patients.

Through bone marrow and peripheral blood examination, we found that the patient had a significant increase in B-lymphocytes. Its main functions include improving secretion of autoantibodies, presenting autoantigens and ensuing reciprocal interactions with T cells, secreting inflammatory cytokines, and promoting the production of ectopic germinal centers. It has been confirmed that T-lymphocytes may induce HBV clearance under the action of B-lymphocytes ⁷ ; therefore, the increase of B-lymphocyte and HBV-DNA during the patient’s treatment may be related to the failure of ETV. At the same time, thrombocytopenia is often related to the high expression of B-lymphocytes, which means better steroid response ⁸ ; that may be the one of the reasons why we succeeded in treating this patient with prednisone alone instead of combined with intravenous immunoglobulin.

Clinicians should consider drug-induced thrombocytopenia in the differential diagnosis of a patient on ETV therapy presenting with unexplained isolated thrombocytopenia. Entecavir-associated thrombocytopenia can mimic primary immune thrombocytopenia (ITP); however, distinguishing these syndromes is important to avoid unnecessary immunosuppressive treatments and to avoid future exposure to the sensitizing drug. Hence, it is important for clinicians to be aware of this adverse drug event and have a general understanding of the common drugs associated with thrombocytopenia.

Conclusions

Since entecavir-associated thrombocytopenia is a reversible cause of thrombocytopenia, which would present with severe thrombocytopenia after starting ETV and resolution after discontinuing the drug, so clinicians should monitor the platelet count during treatment. In the event of a severe decrease in the platelet count, the possibility of the entecavir-associated thrombocytopenia should be considered and the drug should be stopped as soon as possible. Based on this case, platelets count should be checked regularly throughout treatment and detection of B-lymphocytes’ level during early administration of ETV may have certain predictability for entecavir-associated thrombocytopenia. Since we replaced ETV with TDF, and the platelet count did not continue to decline, it may be a feasible option to choose TDF to maintain antiviral treatment when entecavir-associated thrombocytopenia occurs.