A 2-year-old girl is brought to the physician because of abdominal distention and twitching of her feet, which her mother noticed a week ago. The patient has also had a low-grade fever for 5 days. She has not had a bowel movement in 3 days. She was born at term and has been healthy since. She is at the 40th percentile for height and 20th percentile for weight. Her temperature is 38.1°C (100.6°F), pulse is 128/min, and blood pressure is 135/82 mm Hg. Examination shows an irregular palpable mass that crosses the midline of the abdomen. The liver is palpated 3 cm below the right costal margin. There are erratic movements of the eyes. A 24-hour urine collection shows elevated homovanillic acid and vanillylmandelic acid levels. Which of the following is the most likely diagnosis?

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Quizplus · Accepted Answer

Eductional Objective: Opsoclonus-myoclonus is a paraneoplastic syndrome associated with neuroblastoma, the most common extracranial solid neoplasm in children.  The tumor typically arises from the neural crest cells of the adrenal medulla and presents with an abdominal mass and elevated catecholamine breakdown products.

A 2-Year-Old Girl Is Brought to the Physician Because of Abdominal