A Worthwhile Diagnostic Clue: “Cigarette-burn Sign”

Figure 1: A black crusted papular lesion of size 10 mm diameter on the left hypochondrium of her abdomen.A 54-year-old woman presented with a 10-day history of fever, generalized body ache, and a 2-day history of shortness of breath. On examination, she was conscious, cooperative, and tachypneic with a respiratory rate of 22 breaths/min. Her temperature was 101.5°F, blood pressure 110/74 mmHg, pulse rate 110 beats/min, and oxygen saturation was 91% on room air. On investigations, she had mild thrombocytopenia, and slightly elevated serum urea, creatinine, and liver enzyme levels. The chest radiograph showed bilateral haziness. On reevaluation, she was found to have a black crusted papular lesion of size 10 mm diameter on the left hypochondrium of her abdomen [Figure 1]. The patient was totally unaware of this lesion. What is your diagnosis? What this sign is called? ANSWER Scrub typhus is endemic in the Asian region and caused by intracellular Gram-negative coccobacilli, Orientia tsutsugamushi. Humans are accidentally infected, usually in the rainy season by the bite of the larval stage of infected trombiculid mites or chiggers. The clinical presentation of scrub typhus is typically associated with constitution symptoms like fever, rash, myalgia, eschar, and lymphadenopathy. Apart from these symptoms, life-threatening complications can develop, i.e., acute respiratory distress syndrome, thrombocytopenia, shock, encephalitis, and hepatic and renal dysfunctions.[1,2] Mite forms a pathognomic mark "eschar" at the inoculating site of the bite. Eschar is punched necrotic ulcer with a central blackened scab resembling the skin burn of a cigarette butt or the "cigarette-burn sign." The eschars are painless and nonitchy; hence, most of the patients are unaware of it. The reported incidence of eschar is from 46% to 85%.[3] The eschar is usually seen in warm areas of the body which are usually covered with cloths, including the abdomen, back, perineum, inguinal region, axilla, and underneath the breasts. This patient tested positive for IgM scrub typhus with an enzyme-linked immunosorbent assay (ELISA) test. Fever workups for malaria, leptospirosis, and typhoid were negative. A diagnosis of scrub typhus fever with bilateral pneumonitis was made. She was managed with oxygen, injectable doxycycline, azithromycin, and supportive care and dramatically improved with treatment. Immunofluorescence assay is the gold standard, but the Weil–Felix test and scrub typhus IgM ELISA are more commonly used diagnostic tests.[3] Doxycycline is the drug of choice. Eschar or "cigarette-burn mark" is an important diagnostic clue for scrub typhus which is often unnoticed by both the physician and patient.[2,3] Hence, careful examination of the patient to search for "eschar" or "cigarette-burn mark" in a suspected case of scrub typhus is of utmost importance, as early diagnosis and installation of prompt treatment can prevent life-threatening complications. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.