Case 2: A three-year-old boy with fever and neck pain

An unimmunized three-year-old boy with a history of infantile myofibromatosis presented to the emergency department with a four-day history of fever, irritability and neck pain. He had no recent illness, sick contacts or travel. On examination, he was febrile, with neck rigidity and bilateral injected conjunctivae. No oral changes, lymphadenopathy, rashes or extremity changes were noted. Initial investigations revealed an elevated white blood cell count (18.9×109/L) with neutrophilia (15.4×109/L). Due to the child's unimmunized status, concern for vaccine-preventable disease was high. A lumbar puncture was performed, and intravenous cefotaxime and vancomycin were initiated for possible meningitis. The cerebrospinal fluid analysis, including Gram stain and culture, was negative. Twenty-four hours into the hospital admission (the child's fifth febrile day), fever and neck rigidity persisted. A neck radiograph showed thickening in the retropharyngeal space. Findings on a computed tomography (CT) scan of the neck were consistent with a parapharyngeal abscess (Figures 1 and 2). The otolaryngology service recommended continuing intravenous antibiotics because the abscess was not amenable to surgical drainage. However, the child remained febrile and developed cervical adenopathy, dysphagia, dry cracked lips and an erythematous macular rash on his torso. A clinical diagnosis was made. Computed tomography image (coronal view) Computed tomography image (sagittal view). The tip of the arrows point to a hypodense area in the right parapharyngeal space and soft-tissue thickening in the retropharyngeal space Once the child developed prominent right anterior cervical chain lymphadenopathy with nodes >1.5 cm, bilateral hand edema and the erythematous macular rash extended to the lower extremities, the diagnosis of Kawasaki disease (KD) was made. Intravenous immunoglobulin (IVIG) at a dose of 2 g/kg was administered as soon as possible and high-dose acetylsalicylic acid (ASA) (80 mg/kg/day to 100 mg/kg/day) was initiated. An echocardiogram identified no coronary artery changes or other abnormalities. Ancillary investigations revealed an elevated C-reactive protein level (97.9 mg/L) and an elevated erythrocyte sedimentation rate (95 mm/h). The patient's albumin level was low (22 g/L). All cultures (cerebrospinal fluid, blood and urine) were negative at 48 h. Alanine aminotransferase and alkaline phosphatase levels, and urinalysis were all normal. Following one dose of IVIG, the child's fever abated. Within 48 h, his irritability and neck rigidity had resolved. He was discharged home on a lower dose of ASA (3 mg/kg/day to 5 mg/kg/day) for six weeks and had follow-up appointments with cardiology and infectious diseases specialists. No coronary aneurysms developed. KD is a systemic vasculitis syndrome of unknown etiology that primarily affects young children and infants. The lack of a diagnostic test requires clinicians to rely on a classic pattern of signs and symptoms for diagnosis. A clinical diagnosis of KD is made in patients experiencing fever without identifiable cause for >5 days, in addition to at least four of five other criteria. These criteria include bilateral nonexudative conjunctivitis, lip and oral cavity changes, peripheral extremity changes, polymorphous exanthem and cervical lymphadenopathy (at least one node >1.5 cm in diameter). Changes to the lips and oral cavity include erythematous or cracked lips, as well as a ‘strawberry tongue’. Changes to the peripheral extremities include erythema and edema in the acute phase and periungual desquamation in the chronic phase (1). Laboratory findings, including elevated erythrocyte sedimentation rate and C-reactive protein, leukocytosis, thrombocytosis, hypoalbuminemia and sterile pyuria, are commonly observed in KD, although these investigations are not useful in making the diagnosis. KD remains a clinical diagnosis (1). In many cases of KD, the dominant presentation is that of a head and neck infection, such as retropharyngeal abscess. Patients present with fever and symptoms characteristic of deep-space neck infection including neck pain, neck rigidity and trismus. CT findings may include hypodense lesions or low-attenuation areas suggestive of abscess (Figures 1 and 2) (2). The hypodense abscess-like lesions on CT can be misleading. These areas should not be considered to be an infectious process, but rather an inflammatory response associated with KD (2). This is supported by the fact that, in many cases, no abscess cavity is identified and no fluid is obtained from surgical drainage of the retropharyngeal space (2). The complications of KD may be severe, with a 15% to 25% risk of coronary artery dilation or aneurysm in untreated children. These complications can lead to sequelae including thrombosis, myocardial infarction, dysrhythmias or sudden death (1). Treatment includes a single dose of IVIG (2 g/kg) and high-dose ASA (80 mg/kg/day to 100 mg/kg/day) until the patient defervesces. The timely provision of IVIG within a seven- to 10-day window of fever onset reduces the risk of cardiovascular complications from 15% to 25%, to <5% (1). By recognizing that KD can present with unusual clinical, laboratory and imaging findings, physicians may consider the diagnosis sooner, ultimately decreasing the risk of cardiac morbidity and mortality in affected children. In a child who has fever without focus >5 days and meets two principal criteria, a diagnosis of KD should be considered. KD often presents as head and neck manifestations including retropharyngeal abscess, tonsillitis and cervical adenitis. In a confirmed case of KD, a hypodense abscess-like lesion on CT should be considered to be a result of an inflammatory rather than infectious process. The authors acknowledge the contributions of Dr Samarjeet Bhandal (Department of Radiology, University of Calgary, Calgary, Alberta) and Dr Andrew McRae (Department of Emergency Medicine, University of Calgary).

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