A 40-year-old male presented with history of fever, headache and myalgia for 1-week duration. On examination, there was eschar on the left lateral aspect of the abdomen (Figure 1). He was febrile and vitals were stable. The systemic examination was normal. His haemogram showed leukocytosis with normal platelet count. The Weil-Felix test was positive for scrub typhus. The patient recovered completely with doxycycline (100 mg bid PO for 7 days) treatment.

Scrub typhus is an acute febrile illness caused by Orientiatsutsugamushi, which is transmitted to humans by the bite of a larval-stage trombiculid mite or chigger. The eschar develops at the site of inoculation of the organism due to ischaemia and perivascular lymphoplasmocytic reaction, leading to vasculitis.

The eschar, in its early stages, appears as a firm, non-pruritic, erythematous papule. It then enlarges and develops a central vesicle containing clear or opaque fluid. The vesicle eventually ruptures forming a dark brown or black crust over the lesion, the characteristic of an eschar. An area of erythema often surrounds the lesion. The lesion is generally painless.

The eschar generally persists for 3–4 weeks and heals to form a smalldepressed scar¹. The common areas for eschar formation are usually the moist areas of the body. The presence of eschar helps in the clinical diagnosis of scrub typhus.

The differential diagnosis for isolated ulcers and eschars includes both non-infectious and infectious aetiologies^1,2 (Table 1). The eschar is the single most useful diagnostic clue and is pathognomonic for O. tsutsugamushi, but it is seen in less than 10% of cases in the Indian subcontinent³.

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