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LETTER TO EDITOR
Year : 2021  |  Volume : 22  |  Issue : 2  |  Page : 174-176

“Mite bite” sign: A novel atypical eschar of pediatric scrub typhus


1 Department of Pediatrics, All India Institute of Medical Sciences, (AIIMS), Mangalagiri, Andhra Pradesh, India
2 Department of Pediatrics, JIPMER, Karaikal, Puducherry, India

Date of Submission01-Jul-2020
Date of Decision14-Jul-2020
Date of Acceptance25-Nov-2020
Date of Web Publication31-Mar-2021

Correspondence Address:
Thirunavukkarasu Arun Babu
Department of Pediatrics, All India Institute of Medical Sciences, (AIIMS), Mangalagiri, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpd.IJPD_109_20

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How to cite this article:
Babu TA, Narayanasamy DK. “Mite bite” sign: A novel atypical eschar of pediatric scrub typhus. Indian J Paediatr Dermatol 2021;22:174-6

How to cite this URL:
Babu TA, Narayanasamy DK. “Mite bite” sign: A novel atypical eschar of pediatric scrub typhus. Indian J Paediatr Dermatol [serial online] 2021 [cited 2021 Apr 22];22:174-6. Available from: https://www.ijpd.in/text.asp?2021/22/2/174/312822



Sir,

Scrub typhus (ST) is a mite borne acute febrile illness caused by the bacterium, Orientia tsutsugamushi. ST is transmitted by the bite of larval form of trombiculid mite known as chiggers. Eschar is a pathognomonic skin finding in ST which is characterized by a black necrotic lesion with surrounding erythema that develops at the inoculation site due to mite bite.[1] The presence of this typical dermatological finding is critical to make a clinical diagnosis and to start antibiotics early to prevent morbidity and mortality in ST. However, there can be morphological variants of eschar.[2],[3] We report a unique atypical eschar which were identified in children with serologically proven ST.

Our index case was an 11-year-old boy who presented with fever for 10 days without any focus. Examination revealed a painless black circular dry scab surrounded by raised erythema in the left axillary region, consistent with “typical eschar” of ST [black circle; [Figure 1]. He also had left tender axillary lymphadenopathy. His IgM by ELISA for ST was positive (Optical density OD: 2.1) and he became afebrile after 48 h of oral doxycycline. We also noted a characteristic lesion clearly different from classical eschar. This lesion was an umbilicated painless papule with surrounding erythema noted in left axilla a few centimetres below the site of classic eschar [black arrow; [Figure 1]. These lesions never progressed into a “classic eschar” and resolved within 7 days of starting oral doxycycline. We also noted similar lesions [Figure 2], [Figure 3], [Figure 4] in other unrelated children with IgM ELISA positive ST but without typical eschar. These lesions were raised papules with central depression associated with surrounding erythema mostly located on the trunk and axilla. All these lesions disappeared within 7–10 days of resolution of fever without leaving any scar. The clinical summary of these cases with atypical eschar are tabulated in [Table 1].
Figure 1: A typical eschar (black circle) and atypical eschar (black arrow) in the same patient

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Figure 2: An atypical eschar in the axillary region

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Figure 3: An atypical eschar in the hip region

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Figure 4: An atypical eschar in the shoulder region

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Table 1: Comparative clinical characteristics of cases with atypical eschar

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Literature search revealed that chiggers attach to the host at a suitable site using their sharp mouth parts (chelicerae) and make a feeding tube (stylostome) with the tick cement proteins. The salivary secretion injected through this tube dissolves the host tissue, which is then sucked back by these mites. During this chigger feeding process, O. tsutsugamushi, present in the salivary glands of the mites is released into the host tissue. Later, mites detach themselves voluntarily.[4]

The atypical lesions found represent the site of 'mite bite modified by the allergic response mounted by the body. These lesions may or may not develop into a typical eschar and can disappear spontaneously within few days, similar to typical eschar.[2],[5]

Eschar is a valuable sign to clinically diagnose ST even before the serology becomes positive.[1],[2] This “Mite bite” sign may be a form of “atypical eschar” and could be a vital clue in making a clinical diagnosis of ST and active search for these atypical lesions should be done in all suspected cases. More studies with detailed workup including biopsy and polymerase chain reaction of these lesions are needed to understand the characteristics and to conclusively prove its association with ST.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Reller ME, Dumler JS. Scrub typhus (Orientia tsutsugamushi). In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, editors. Nelson's Textbook of Pediatrics. 20th ed. Philadelphia, USA: Elsevier; 2016. p. 1504-5.  Back to cited text no. 1
    
2.
Arun Babu T, Vijayadevagaran V, Ananthakrishnan S. Characteristics of pediatric scrub typhus eschar in South Indian Children. Pediatr Dermatol 2017;34:124-7.  Back to cited text no. 2
    
3.
Park J, Woo SH, Lee CS. Evolution of eschar in scrub typhus. Am J Trop Med Hyg 2016;95:1223-4.  Back to cited text no. 3
    
4.
Elliott I, Pearson I, Dahal P, Thomas NV, Roberts T, Newton PN. Scrub typhus ecology: A systematic review of Orientia in vectors and hosts. Parasit Vectors 2019;12:513.  Back to cited text no. 4
    
5.
Kundavaram AP, Jonathan AJ, Nathaniel SD, Varghese GM. Eschar in scrub typhus: A valuable clue to the diagnosis. J Postgrad Med 2013;59:177-8.  Back to cited text no. 5
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