Scrub typhus is a common cause of febrile illness in South East Asia resulting from a mite-borne infection with Orientia tsusugamushi. After a chigger bite, an eschar forms at the bite site in about half of primary infections and in a lesser proportion of secondary infections. The eschar begins as a small papule, enlarges, undergoes central necrosis, and acquires a blackened crust to form a lesion resembling a cigarette burn. It is usually found in an exposed area of the lower limbs but also in the groin and axilla. We described 2 cases of children with scrub typhus in whom the eschar situated in the genitalia was missed during the initial physical examination.
The presence of the eschar aids in early diagnosis of scrub typhus and treatment.
A 12-year-old Malay girl was referred to our hospital with a 5-day history of fever with chills and rigors. She also complained of having cough and vomiting as well as a maculopapular rash over the entire body. Examination revealed that her temperature was 40°C and her vital signs were stable with pulse rate of 104/min and blood pressure of 118/65 mm Hg. There was no lymphadenopathy or hepatomegaly. Examination of other systems was normal. She had a full blood count which showed thrombocytopenia of 73,000/mL with leukocyte count of 5.7 × 103/mL and hematocrit of 36%. A preliminary diagnosis of dengue fever was made and she was treated symptomatically with antipyretics.
Her fever persisted 2 days after admission prompting a thorough examination of the child that revealed an eschar sized 1.0 × 1.0 cm on her left labia majora (Fig. 1, left). A diagnosis of scrub typhus was made and a 5-day course of doxycyline was commenced. She became afebrile 24 hours after starting treatment and was subsequently discharged well. The immunoperoxidase test for scrub typhus is strongly positive (Ig M titer of 1/1600).
A 6-year-old Malay boy presented to our hospital with 10 days of high fever with chills and rigor. He complained of nonproductive cough, sore throat, and abdominal pain. He also had loose stools 1–2 times per day without mucus or blood in the stool. He had visited a general practitioner 4 days before admission and an antibiotic had been prescribed without improvement. The full blood count showed mild thrombocytopenia of 117,000 per mm3 and a leukocyte count of 8.3 × 103 per mL.
On examination, the child had a temperature of 39.2°C. His blood pressure was 100/68 mm Hg and pulse rate of 125/min. His lips were dry and cracked with his tongue coated. The throat was injected and there were multiple shortly cervical lymph nodes. Examination of the abdomen revealed hepatomegaly of 4 cm and splenomegaly of 2 cm. There were no other abnormalities.
An initial diagnosis of viral infection was made and the child was treated symptomatically. Because his fever persisted a more thorough physical examination was performed. A 0.5 × 0.5 cm sized eschar was found on his left scrotum that was missed during the previous examination (Fig. 1, right). A provisional diagnosis of scrub typhus was made and a 5-day course of doxycycline was prescribed. The child became afebrile 24 hours after starting treatment and was subsequently discharged well. The Immunoperoxidase test was positive with 4-fold increase in Ig G titer from 1/200 to 1/1600 in blood specimens taken 8 weeks apart.
Scrub typhus is associated with vasculitis secondary to endothelial injury as a result of infection by Orientia tsutsugamushi, an obligate intracellular Gram-negative bacterium. It is transmitted to humans during the bite of a larval trombiculid mite, known popularly as a chigger. The spectrum of illness in children is similar to the adult counterpart as well describe in many studies.
Historically, diagnosis of scrub typhus is aided by finding an eschar on an exposed part of the body. Confirmation of scrub typhus infection in humans is usually made by demonstrating an increase in serum antibodies against O. tsutsugamushi either by a single high titer of Ig M or a 4-fold increase in Ig G antibodies during convalescence.1 Because of a delay between the onset of the illness and an increase in the titer of specific antibodies, finding an eschar is important in making a provisional diagnosis.
The eschar usually appears within 2 days of the chigger's bite and appears as a skin papule that slowly sloughs to become a shallow ulcer. Subsequently, the ulcer is covered by a black crust that can be absent in moist skin folds. The mite had a predilection for biting pressure points such as boots top and belt lines.2,3 Other moist skin folds such as the groin, popliteal fossa, buttock, and axillae are also common sites for eschar. Lau et al4 also reported a case of eschar in the perineum region of an elderly lady in Taiwan. Reports of occurrence of eschar in pediatric patients in Thailand vary from 7% to 75% in different series.5–7 A recent review by Kim et al3in Korea reported eschar occurrence in up to 92% of 176 laboratory-confirmed scrub typhus cases.
In conclusion, a high index of suspicion and a thorough physical examination is important for early presumptive diagnosis and prompt antibiotic therapy for scrub typhus in endemic areas.
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