A 28-year-old woman from Delhi presents with a 5-day history of fever (38.5°C), right upper quadrant pain, and jaundice. She reports nausea, vomiting, and dark urine. On examination, she is febrile and icteric with marked right upper quadrant tenderness and hepatomegaly (4 cm). Laboratory results: total bilirubin 6.5 mg/dL (unconjugated 3.2 mg/dL, conjugated 3.3 mg/dL), AST 1240 U/L, ALT 1680 U/L, ALP 180 U/L, albumin 4.1 g/dL. Abdominal ultrasound shows hepatomegaly with heterogeneous echotexture, no gallstones, and normal bile ducts. Serologies: anti-HAV IgM positive, HBsAg negative, anti-HCV negative. What is the most likely diagnosis?

Explanation

## Clinical Reasoning **Key Point:** The combination of acute hepatitis presentation (fever, RUQ pain, jaundice) with markedly elevated transaminases (ALT > AST), preserved synthetic function, and positive anti-HAV IgM serology is diagnostic of acute hepatitis A. ### Pattern Recognition: Hepatocellular vs. Cholestatic Jaundice | Feature | This Case | Hepatocellular | Cholestatic | |---------|-----------|---|---| | AST/ALT | 1240/1680 | **>>** ALP | << ALP | | ALP | 180 | Normal or mildly ↑ | **Markedly ↑** | | Bilirubin | Mixed (3.2 unconj, 3.3 conj) | Both elevated | Predominantly conjugated | | Imaging | Normal ducts, hepatomegaly | Parenchymal injury | Ductal obstruction | | **Diagnosis** | **Hepatocellular** | ✓ Fits | ✗ Does not fit | **High-Yield:** In acute viral hepatitis, **ALT > AST** and **transaminases >> ALP** (often >1000 U/L). This is the hallmark of hepatocellular injury. ### Serological Diagnosis **Anti-HAV IgM positive** = **acute hepatitis A infection**. This is the gold standard for diagnosis. - **Anti-HAV IgG** (not mentioned) would indicate past infection or immunity - **IgM appears early** (within days of symptom onset) and persists for ~6 months - **IgG appears later** and provides lifelong immunity **Clinical Pearl:** Hepatitis A is a **self-limited, non-progressive infection**. There is no chronic carrier state. Fulminant hepatic failure occurs in <1% of cases (higher in older patients or those with pre-existing liver disease). ### Why Hepatitis A? 1. **Epidemiology:** Young adult, endemic area (Delhi), likely fecal-oral transmission 2. **Acute presentation:** Fever, RUQ pain, jaundice over 5 days = acute hepatitis 3. **Laboratory pattern:** Massive transaminitis (ALT 1680), ALT > AST, normal albumin = acute hepatocellular injury with preserved synthetic function 4. **Serological confirmation:** Anti-HAV IgM positive = definitive diagnosis 5. **Imaging:** Normal bile ducts rule out biliary obstruction; hepatomegaly with heterogeneous echotexture is typical of acute hepatitis **Mnemonic:** **ACUTE HAV** — **A**cute onset (days), **C**ytolytic pattern (ALT >> ALP), **U**nconjugated + conjugated bilirubin, **T**ransaminases >1000, **E** (no) **H**BsAg or anti-HCV, **A**nti-HAV IgM positive, **V**iral hepatitis. ### Natural History ```mermaid flowchart TD A[HAV Exposure]:::outcome --> B[Incubation: 15-50 days]:::outcome B --> C[Acute Hepatitis Phase]:::action C --> D{Fulminant?}:::decision D -->|No 99%| E[Complete Recovery]:::outcome D -->|Yes <1%| F[Fulminant Hepatic Failure]:::urgent E --> G[Lifelong Immunity]:::outcome ```