A 4-year-old boy presented with a 10-day history of vomiting. This was later associated with drooling and mild abdominal distention. No fever, rash, or diarrhea were noted.
On physical examination, he was afebrile and in no apparent distress. Diffuse petechial lesions were seen in the soft palate, the abdomen was distended without organomegaly, and pitting edema was present in both lower extremities.
Initial laboratory studies showed the following values: hemoglobin, 131 g/L; white blood cell count, 16.7×109/L; eosinophils, 2.0×109/L; and platelet count, 258×109/L. Results of urinalysis were normal, with no evidence of proteinuria. Results of liver function tests were likewise normal. Electrolyte values were as follows: sodium, 128 mmol/L; potassium, 4.2 mmol/L; blood urea nitrogen, 4.3 mmol/L (12 mg/dL); creatine, 40 mol/L; osmolality, 268 mmol/kg; and total protein, 24 g/L. Chest roentgenograms were normal. Abdominal sonography (Figs 1 and 2) and study of the upper gastrointestinal tract (Fig 3) were performed.