Hepatitis C

01Pathophysiology

Hepatitis C virus is a single-stranded, positive-sense RNA virus belonging to the Flaviviridae family. It is a hepatotropic virus, meaning it preferentially infects hepatocytes. The virus enters the hepatocyte primarily through receptor-mediated endocytosis involving several co-receptors, including CD81, SR-B1, claudin-1, and occludin. Once inside, HCV hijacks the host cell's translational machinery to replicate its genome using an RNA-dependent RNA polymerase (RdRp), which is a critical concept because this polymerase lacks proofreading ability. This leads to an extremely high mutation rate, generating viral quasispecies that constantly evade the host immune response.

Understanding why HCV becomes chronic in 75 to 85% of cases is central to exam questions. The virus itself is not directly cytopathic. Instead, liver injury is immune-mediated: CD8+ cytotoxic T lymphocytes and natural killer (NK) cells recognize and attack infected hepatocytes. However, because the virus mutates so rapidly, the adaptive immune response is always "one step behind," unable to fully clear the infection. This ongoing, low-grade immune assault creates a cycle of hepatocyte injury, inflammation, and regeneration that, over 20 to 30 years, drives progressive hepatic fibrosis and eventually cirrhosis in approximately 20 to 30% of chronically infected patients. Cirrhosis, in turn, is the major risk factor for hepatocellular carcinoma (HCC), which develops at a rate of about 1 to 4% per year in cirrhotic patients.

The extrahepatic manifestations of HCV are very testable because they serve as diagnostic clues. HCV stimulates B lymphocyte proliferation and the production of cryoglobulins (type II mixed cryoglobulinemia). These immune complexes deposit in small vessels, leading to leukocytoclastic vasculitis, palpable purpura, arthralgias, and renal disease, particularly membranoproliferative glomerulonephritis (MPGN). HCV is also the most commonly tested association with porphyria cutanea tarda (PCT), where disrupted heme biosynthesis causes photosensitive blistering skin lesions. Additionally, HCV-driven chronic B-cell stimulation is linked to an increased risk of B-cell non-Hodgkin lymphoma.

02Classification and Clinical Manifestation

03Diagnostic Workup

The diagnostic approach to Hepatitis C follows a strict two-step algorithm, and understanding this sequence is what exam questions test most frequently.

Step 1 is always the anti-HCV antibody test. This is the screening test recommended by public health guidelines for all adults aged 18 to 79, as well as for any patient with risk factors regardless of age. A positive result means the patient has been exposed to HCV at some point, but it cannot tell you whether the infection is currently active or was cleared in the past. Importantly, the antibody typically takes 4 to 10 weeks to become detectable after exposure, creating a "window period." This is a tested concept: if a patient presents with acute symptoms and a recent exposure (for example, a needlestick 2 weeks ago), the anti-HCV may still be negative. In this scenario, you must proceed directly to HCV RNA.

Step 2 is the HCV RNA by PCR (quantitative viral load). This is the confirmatory test and the earliest detectable marker, turning positive as early as 1 to 2 weeks after exposure. A positive HCV RNA confirms active infection. If the anti-HCV is positive but HCV RNA is negative, the patient has either spontaneously cleared the virus or was successfully treated in the past. This distinction is heavily tested.

There is an important exception in immunocompromised patients (such as those with HIV, organ transplant recipients, or patients on hemodialysis). These patients may fail to mount an antibody response, so anti-HCV can be falsely negative despite active infection. In any immunocompromised patient with unexplained liver disease or elevated transaminases, go directly to HCV RNA without waiting for antibody results.

Once active infection is confirmed, HCV genotyping is performed to guide selection and duration of DAA therapy. While pan-genotypic regimens have reduced the clinical weight of genotyping, it still appears on exams. Additionally, all patients should undergo fibrosis staging using non-invasive methods such as transient elastography (FibroScan) or calculated scores like FIB-4 or APRI. These determine the urgency of treatment and whether HCC surveillance (ultrasound every 6 months) is warranted. Liver biopsy, while the gold standard for fibrosis assessment, is rarely performed in practice.

Before starting treatment, always screen for Hepatitis B co-infection (HBsAg, anti-HBc, anti-HBs). DAA therapy can cause HBV reactivation, which has led to fulminant hepatitis and death. This is a high-yield safety point.

04Management and Treatment

Acute management. In a patient diagnosed with acute HCV infection, the recommended approach is watchful waiting for 12 to 16 weeks with repeat HCV RNA testing, because 15 to 25% of patients will spontaneously clear the virus. If HCV RNA remains detectable beyond this window, the infection is considered chronic and treatment should be initiated. There is no role for interferon-based therapy in modern management; this is an outdated answer choice that still appears as a distractor.

Chronic HCV treatment. The current standard of care revolves entirely around direct-acting antivirals (DAAs). All patients with confirmed chronic HCV (positive HCV RNA for more than 6 months) should be treated regardless of fibrosis stage, with very few exceptions. The two most commonly tested pan-genotypic regimens are:

Glecaprevir/Pibrentasvir (Mavyret): Given as three tablets once daily for 8 weeks in treatment-naive patients without cirrhosis. This is the shortest FDA-approved pan-genotypic regimen and is frequently the tested "best answer" for an uncomplicated, treatment-naive patient.

Sofosbuvir/Velpatasvir (Epclusa): Given as one tablet once daily for 12 weeks. This is effective across all genotypes and is generally well-tolerated with minimal drug interactions.

For genotype 1 (the most common genotype in North America and Europe), Ledipasvir/Sofosbuvir (Harvoni) remains a valid option. It can be shortened to 8 weeks if the patient is treatment-naive, non-cirrhotic, and has an HCV RNA level below 6 million IU/mL.

Decompensated cirrhosis requires careful regimen selection. Protease inhibitors (any drug ending in "-previr," such as glecaprevir or voxilaprevir) are contraindicated in decompensated cirrhosis (Child-Pugh B or C) because they are hepatically metabolized and can worsen liver failure. The recommended regimen in this setting is Sofosbuvir/Velpatasvir with or without Ribavirin. If Ribavirin is added, monitor for hemolytic anemia. These patients should also be evaluated for liver transplantation.

Treatment endpoint. The goal of therapy is sustained virologic response (SVR), defined as an undetectable HCV RNA 12 weeks after completion of treatment. Achieving SVR is considered a virologic cure. However, patients who had cirrhosis prior to treatment must continue lifelong HCC surveillance with abdominal ultrasound every 6 months, even after achieving SVR, because the risk of hepatocellular carcinoma persists.

Contraindications and cautions. Ribavirin is teratogenic (Category X) and absolutely contraindicated in pregnancy and in partners of pregnant individuals. Two forms of contraception are required during and for 6 months after Ribavirin use. Sofosbuvir should not be combined with Amiodarone due to the risk of severe symptomatic bradycardia. Before starting any DAA, screen for HBV co-infection to prevent reactivation.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common trap with Hepatitis C on licensing exams involves misinterpreting the anti-HCV antibody result. Students frequently see a positive anti-HCV and assume the patient has active infection, jumping straight to treatment. This is wrong. A positive anti-HCV only means the patient was exposed at some point. The next required step is HCV RNA by PCR to determine whether there is active viremia. If HCV RNA is negative, the patient has cleared the virus (either spontaneously or through prior treatment) and does not need therapy. Expect vignettes designed to punish this exact mistake.

The second major trap involves immunocompromised patients. In HIV co-infected, transplant, or hemodialysis patients, the anti-HCV antibody can be falsely negative because of impaired humoral immunity. When an immunocompromised patient has unexplained transaminase elevations or liver disease, the correct move is to order HCV RNA directly, bypassing the antibody test entirely. Choosing anti-HCV as the initial test in this population is a designed wrong answer.

A third tested concept is the association between HCV and extrahepatic diseases. When a vignette describes palpable purpura, arthralgias, and renal insufficiency with low complement levels, think mixed cryoglobulinemia and look for HCV as the underlying etiology. Similarly, porphyria cutanea tarda (blistering skin lesions on sun-exposed areas with elevated urine uroporphyrins) should prompt you to screen for HCV. These connections are frequently tested because they assess your ability to link systemic findings back to a hepatotropic virus.

Finally, remember that protease inhibitors are contraindicated in decompensated cirrhosis. Vignettes will describe a patient with Child-Pugh B or C cirrhosis and offer Glecaprevir/Pibrentasvir as a tempting answer choice because it is the shortest regimen. The correct choice for decompensated disease is Sofosbuvir/Velpatasvir (with or without Ribavirin). Also, never forget to screen for HBV before starting any DAA, as HBV reactivation during HCV treatment is a reported and potentially fatal complication. The core competency being tested across all these scenarios is your ability to follow a disciplined diagnostic algorithm (antibody then RNA, not the reverse), recognize extrahepatic clues that point to HCV, and select the correct regimen based on the patient's liver function status.