A 42-year-old, otherwise healthy, male was admitted to the emergency room with a four-day history of malaise, myalgia, and high-grade fever. Laboratory tests showed increased liver enzymes (aspartate aminotransferase [AST] 2216 U/L and alanine aminotransferase [ALT] 1611 U/L), but normal bilirubin. Dengue Fever (DF) rapid test (NS1) and serology (ELISA IgM and IgG) were performed with negative results. Two days later the patient developed jaundice (total bilirubin 6.36 mg/dL and direct bilirubin 5.60 mg/dL) with a decrease in platelet count (52000 /mm3), normal international normalized ratio (INR) (0.85), and moderate proteinuria. At that time, abdominal ultrasonography showed hepatomegaly. Serology for viral hepatitis, Epstein-Barr virus, and Cytomegalovirus were negative. Dengue serology was repeated, and found positive, suggesting DF-related hepatitis. Despite an uncertain patient report of prior YF vaccination, YF polymerase chain reaction (YF-PCR) was performed considering the epidemiological risk and YF outbreak context. The patient was discharged after one week with improvement of laboratorial parameters (AST 259 U/L, ALT 638 U/L, alkaline phosphatase 153 U/L, platelets 294000 /mm3, and total bilirubin 2.25 mg/dL). The YF-PCR result was not available prior to discharge.
After 40 days, he was readmitted to the hospital with persistent fatigue, jaundice, and pruritus. Liver enzymes and bilirubin had increased (total bilirubin 19.2 mg/dL, AST 1037 U/L, ALT 2289 U/L, gamma-glutamyl transferase [GGT] 669 U/L, and INR 1.05). Extensive workup including serologies, ceruloplasmin, and ferritin was performed, but not indicative of a specific etiology. A hypothesis of autoimmune liver disorder was discarded by negative autoantibodies (i.e., anti-nuclear, anti-smooth muscle, and anti-mitochondria antibodies) and normal serum gamma-globulin. Liver biopsy demonstrated lobular hepatitis with mild neutrophilic infiltration (Figure 1). The remaining parenchymal cells showed frequent hepatocyte ballooning, macro- and microvacuolar steatosis, and rare apoptotic bodies. The patient was discharged again after a small decrease in total bilirubin without a definitive diagnosis. A follow-up hepatology appointment was scheduled for five days later. 
Upon hepatologist consultation, it was found that the YF-PCR ordered during the first hepatitis episode was positive, thus corroborating the suspicion of relapsing hepatitis due to YF. A pathological review was performed, including YF virus immunohistochemistry stain, but it was negative. The patient was started on ursodeoxycholic acid (10 mg/kg) and within three days improved his pruritus and bilirubin levels. In the two-week follow-up period, liver enzymes were normal, and the medication was suspended.