Travel-acquired Scrub Typhus Infection Masked by Dengue Fever in a Patient from Nonendemic Area

Sir,

Scrub typhus is endemic to the sub-Himalayan region and southern states of India.[1,2] Dengue is prevalent throughout the country. Both infections are common during the postmonsoon months and present as acute febrile illness with rash. A necrotic eschar at the inoculating site of the mite is hallmark of scrub typhus.[1] Complications include myocarditis, pericarditis, cardiac arrhythmia, acute renal failure, acute liver failure, and rarely pancreatitis.[1,2] Scrub typhus infection can be missed in the presence of coinfection with dengue as the clinical symptoms and signs of both these infections overlap.[3,4]

A 45-year-old male from Uttar Pradesh, India, was referred to us with a history of high-grade fever, pedal edema, facial puffiness, and shortness of breath of 7-day duration. The initial investigations revealed leukopenia with thrombocytopenia, and ELISA test for dengue nonstructural 1 antigen was positive. He had visited the sub-Himalayan state of Uttarakhand before the onset of fever. On physical examination, he was febrile (101.3°F) and vital signs were stable. A necrotic eschar was present on the dorsum of the penis [Figure 1]. Chest auscultation revealed bilateral crepts with wheeze. Laboratory investigations showed leukocytosis (11.8 × 10⁹/L), thrombocytopenia (71 × 10⁹/L), elevated serum bilirubin (3.0 mg/dl), transaminases (aspartate aminotransferase [AST] 257 U/L; alanine transaminase [ALT] 154 U/L), alkaline phosphatase (240 U/L), lipase (862 U/L), and amylase (338 U/L) levels. Chest radiograph showed bilateral bronchopneumonia. Computerized tomography scan of the abdomen revealed diffuse parenchymal enlargement of the pancreas with blurring of its margin suggestive of pancreatitis. ELISA test for scrub typhus IgM antibodies was positive.

Figure 1.

A black necrotic eschar over the dorsum of the penis (indicated by arrow)

A diagnosis of coinfection with dengue and scrub typhus with bilateral pneumonia and hepatic and pancreatic dysfunction was made. He was successfully treated with oral doxycycline 200 mg per day and intravenous ceftriaxone (1 g × Q 8 hourly) for 7 days.

Watt et al.[4] have attempted to differentiate both the two infections on the basis of clinical and laboratory features. They observed that bleeding gums, thrombocytopenia, and leukopenia favor a diagnosis of dengue. In contrast, scrub typhus is associated with leukocytosis and thrombocytopenia. Elevated serum transaminases (serum AST > serum ALT) are seen in both infections. In patients with coinfection, the mean hemoglobin level is lower and the leukocyte count is in normal range when compared to patients with dengue or scrub typhus infection alone. Similarly, the serum ALT and AST levels are higher in patients with coinfection.[5]

Scrub typhus should be considered as a differential diagnosis in patients presenting with acute febrile illness with multiple organ involvement in tropical countries. Empirical therapy with doxycycline should be considered even before the diagnosis is confirmed by serological tests to reduce the risk of serious complications and mortality.[1,2]

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