A 29-year-old man comes to the physician for a routine health maintenance examination. He feels well. He works as a nurse at a local hospital in the city. Three days ago, he had a needlestick injury from a patient whose serology is positive for hepatitis B. He completed the 3-dose regimen of the hepatitis B vaccine 2 years ago. His other immunizations are up-to-date. He appears healthy. Physical examination shows no abnormalities. He is concerned about his risk of being infected with hepatitis B following his needlestick injury. Serum studies show negative results for hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis C antibody. Which of the following is the most appropriate next step in management?

Administer hepatitis B immunoglobulin and 3-dose regimen of hepatitis B vaccine

Revaccinate with 3-dose regimen of hepatitis B vaccine

Revaccinate with two doses of hepatitis B vaccine

Administer hepatitis B immunoglobulin

Administer hepatitis B immunoglobulin and single dose hepatitis B vaccine

Two months after giving birth to a boy, a 27-year-old woman comes to the physician with her infant for a well-child examination. She was not seen by a physician during her pregnancy. Physical examination of the mother and the boy shows no abnormalities. Laboratory studies show elevated titers of hepatitis B surface antigen in both the mother and the boy. Which of the following statements regarding the infant's condition is most accurate?

Significant elevation of transaminases is not expected

Hepatitis B e antigen titer is likely undetectable

Lifetime risk of hepatocellular carcinoma is low

The viral replication rate is low

A 28-year-old man presents to the office with complaints of malaise, anorexia, and vomiting for the past 2 weeks. He also says that his urine is dark. The past medical history is unremarkable. The temperature is 36.8°C (98.2°F), the pulse is 72/min, the blood pressure is 118/63 mm Hg, and the respiratory rate is 15/min. The physical examination reveals a slightly enlarged, tender liver. No edema or spider angiomata are noted. Laboratory testing showed the following: HBsAg Positive IgM anti-HBc < 1:1,000 Anti-HBs Negative HBeAg Positive Anti-HBe Negative HBV DNA 2.65 × 10⁹ IU/L Alpha-fetoprotein 125 ng/mL What is the most likely cause of this patient's condition?

Acute exacerbation of chronic HBV infection

Resolved HBV infection (innate immunity)

A 27-year-old woman who recently emigrated from Brazil comes to the physician because of fever, fatigue, decreased appetite, and mild abdominal discomfort. She has not seen a physician in several years and her immunization status is unknown. She drinks 2 alcoholic beverages on the weekends and does not use illicit drugs. She is sexually active with several male partners and uses condoms inconsistently. Her temperature is 38°C (99.8°F). Physical examination shows right upper quadrant tenderness and scleral icterus. Serology confirms acute infection with a virus that has partially double-stranded, circular DNA. Which of the following is most likely involved in the replication cycle of this virus?

Reverse transcription of viral RNA to DNA

Adhesion of virus to host ICAM-1 receptor

Cleavage of gp160 to form envelope glycoprotein

Bacterial translation of viral DNA

Transcription of viral DNA to RNA in the cytoplasm

A 52-year-old female presents to her primary care physician for medical evaluation prior to an elective hip replacement surgery. She has hypertension and diabetes, both of which are well controlled on oral medications. She also admits to occasional use of recreational injection drugs so a panel of serologies are obtained. Based on the results, the patient is found to have had a previous infection with hepatitis B from which she has fully recovered. Which of the following is a characteristic of the immunoglobulin subtype that most likely binds to hepatitis B core antigen in this patient?

It is only activated by multivalent immunogens

A 32-year-old woman comes to the emergency department for a 2-week history of right upper quadrant abdominal pain. She has also been feeling tired and nauseous for the past 5 weeks. She has a history of depression and suicidal ideation. She is a social worker for an international charity foundation. She used intravenous illicit drugs in the past but quit 4 months ago. Her only medication is sertraline. Her temperature is 37.8°C (100.0°F), pulse is 100/min, and blood pressure is 128/76 mm Hg. She is alert and oriented. Scleral icterus is present. Abdominal examination shows tenderness to palpation in the right upper quadrant. The liver edge is palpated 3 cm below the right costal margin. There is no rebound tenderness or guarding. The abdomen is non-distended and the fluid wave test is negative. She is able to extend her arms with wrists in full extension and hold them steady without flapping. Laboratory studies show: Hemoglobin 13.8 g/dL Leukocytes 13,700/mm3 Platelets 165,000/mm3 Prothrombin time 14 seconds Partial thromboplastin time 35 seconds Serum: Total bilirubin 4.8 mg/dL Direct bilirubin 1.3 mg/dL Aspartate aminotransferase 1852 U/L Alanine aminotransferase 2497 U/L Urea nitrogen 21 mg/dL Creatinine 1.2 mg/dL Hepatitis A IgM antibody Negative Hepatitis B surface antigen Negative Hepatitis B surface antibody Negative Hepatitis B core IgM antibody Positive Hepatitis C antibody Positive Hepatitis C RNA Negative Urine beta-hCG Negative Which of the following is the most appropriate next step in management?

Vaccination against Hepatitis B

Acute hepatitis B for USMLE Step 2 CK: High-Yield Microbiology Lessons

HBV Virology & Transmission - The Viral Blueprint

Virology: An enveloped virus from the Hepadnaviridae family. It has a unique partially double-stranded circular DNA genome and notably encodes a reverse transcriptase for its replication cycle.
Transmission: Spread through parenteral (IV drug use, needlesticks), sexual, and perinatal (vertical) routes. 📌 Mnemonic: B for Blood, Birthing, and Bonking (sexual contact).

Hepatitis B Virus (HBV) Structure

⭐ HBV is the only human DNA virus that replicates via a reverse transcriptase, a key target for antiviral therapy.

Clinical & Pathophysiology - The Host Response

Incubation Period: 1-4 months.
Clinical Phases:
- Prodrome (Serum Sickness-Like Syndrome): Fever, rash, and arthralgia often precede jaundice due to immune complex deposition.
- Icteric Phase: Jaundice, RUQ pain, hepatomegaly, dark urine (bilirubinuria), and pale stools (acholic stools).
Pathophysiology: Liver injury is not directly cytopathic. It is immune-mediated by CD8+ T-cells attacking hepatocytes that express viral antigens.

⭐ The severity of acute illness reflects the vigor of the host's immune response, not the viral load. A strong response causes more damage but effectively clears the virus.

Acute Hepatitis B: Liver Histology

Histology Findings:
- Acute: Panlobular inflammation, ballooning degeneration, and Councilman bodies (apoptotic hepatocytes).
- Chronic: "Ground-glass" hepatocytes (HBsAg accumulation in cytoplasm).

Serological Markers - Decoding the Blood

HBsAg (Surface Antigen): The very first marker to appear in the blood. Its presence indicates an active, ongoing Hepatitis B infection.
HBeAg (e Antigen): Appears shortly after HBsAg. A key indicator of active viral replication and high infectivity.
Anti-HBc IgM (Core Antibody): The first antibody to become detectable. It is the most reliable marker for diagnosing an acute infection.
Window Period: A critical diagnostic gap where HBsAg has disappeared, but the protective Anti-HBs has not yet formed. During this time, Anti-HBc IgM is the sole indicator of a recent infection.
Anti-HBe: Appearance signifies seroconversion, marking a decrease in viral replication and infectivity.
Anti-HBs (Surface Antibody): Its presence indicates recovery and protective immunity. This is the goal of vaccination.
Anti-HBc IgG: Replaces Anti-HBc IgM and persists for life, serving as a marker of past infection.

⭐ The first and most reliable marker of acute Hepatitis B infection is Anti-HBc IgM.

Diagnosis & Management - The Game Plan

Diagnosis: Suspect clinically; confirm with serology showing positive HBsAg and Anti-HBc IgM.
Management: Primarily supportive care. Antivirals (e.g., tenofovir) are reserved for severe, fulminant hepatitis.
Post-Exposure Prophylaxis (PEP): Administer Hepatitis B Immune Globulin (HBIG) and the HBV vaccine series.
Prognosis: Excellent in adults, with >95% achieving complete recovery.

⭐ The risk of developing chronic HBV is inversely proportional to the age of infection: ~90% for neonates vs. <5% for immunocompetent adults.

High-Yield Points - ⚡ Biggest Takeaways

Acute Hepatitis B is a DNA virus, primarily transmitted via parenteral, sexual, and perinatal routes.

The hallmark of acute infection is the presence of HBsAg and anti-HBc IgM.

HBeAg is a key indicator of active viral replication and high infectivity.

The "window period" may show only anti-HBc IgM as positive.

Anti-HBs without other markers signifies immunity from vaccination.

Over 95% of infected adults achieve spontaneous recovery.

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