Morphological Variations and Anatomical Distribution of Atypical Eschars in Pediatric Scrub Typhus: A Prospective Observational Study.

BACKGROUND

Necrotic flexural eschar is a pathognomonic cutaneous marker of scrub typhus (ST). Relying solely on the classic necrotic flexural eschar can result in missed diagnoses when lesions present atypically. This study evaluated the clinical profile and predictors of atypical eschars (ATEs) in children with ST.

METHODS

In this 5-year prospective observational study from South India, children (< 12 years) with serologically confirmed ST (IgM ELISA) were systematically examined for eschars using a standardized whole-body assessment. Eschars were classified as typical eschars (TEs: necrotic ulcer with or without scab) or ATE (non-necrotic papule with umbilication). Children were grouped based on their eschar phenotype. Clinical features, anatomical distribution, laboratory parameters, and outcomes were compared.

RESULTS

Of the 692 confirmed ST cases, 349 (50.4%) children with inoculation site eschars were included. Among them, 261 (74.8%) had TE and 88 (25.2%) had ATE. A total of 398 eschars were identified, as some children had multiple lesions. ATEs were significantly more common in exposed, non-flexural sites, whereas TEs predominantly involved flexural regions, such as the axilla and groin. Independent predictors of ATE included multiple eschars (aOR 2.77; 95% CI 1.16-6.75) and leukocytosis (aOR 2.22; 95% CI 1.21-4.06). Flexural location and regional lymphadenopathy were inversely associated with ATE. Disease severity and clinical outcomes were comparable between the groups.

CONCLUSION

One-fourth of pediatric ST cases with eschars have atypical lesions, which are often multiple, located at exposed sites, and lack regional lymphadenopathy. Diagnostic evaluation must extend beyond flexural folds, as ATEs are clinically and diagnostically equivalent to typical lesions.