A Case of Atypical Kawasaki Disease With Myositis

A 6-year-old Chinese girl presented to our institution with fever of 9 days. Her temperature was persistently above 38.5°C, with a maximum temperature of more than 40°C. This was associated with sore throat and cough. There was no recent travel or sick contact, and her vaccinations were up-to-date with the national immunization schedule. She was initially seen by a family physician and given azithromycin on day 4 of illness. She completed the course of antibiotics, despite developing a pruritic and erythematous maculopapular rash 3 hours after the first dose. The rash first started on the limbs, but became generalized over the next 2 days, spreading to the perineum, trunk, neck, and face. On day 6 of illness, the rash started peeling, and she developed left calf pain as well. She was admitted to another hospital and was treated for a drug-induced rash with 5 doses of intravenous (IV) hydrocortisone, but there was minimal improvement. A red tongue with prominent papillae was also noted at the hospital. She then developed left calf swelling on day 8 of illness. She was treated empirically with IV ceftriaxone and amoxicillin/clavulanic acid and was transferred to our institution on day 9 of illness. Physical examination revealed a febrile child with a temperature of 39.6°C, heart rate of 148 beats per minute , and blood pressure of 104/95 mm Hg. She was lethargic and irritable, but not in distress. Her neck was supple. An erythematous macular rash was noted over her face, trunk, limbs, and perineum, with peeling over these areas as well. The rash had a sandpaper texture and was blanchable. There was no conjunctival injection, but she had red and swollen lips (Figure 1) with a strawberry tongue. The throat and tonsils were slightly injected, but there was no tonsillar hypertrophy or exu-dates. Sub-centimeter cervical lymph nodes were palpable bilaterally. On auscultation of the chest, dual heart sounds were present with no murmurs, and lungs were clear. The abdomen was soft but slightly distended, with tender hepatomegaly measuring 2 cm below the costal margin, as well as shifting dullness. Examination of the limbs revealed mild edema over the feet bilaterally, as well as a swollen left calf (Figure 2), which was warm, tender, and erythematous. She was unable to move the left lower limb or ambulate due to pain. Neurological examination was grossly normal. Tables 1 and 2 summarize the blood investigations and microbiological …