An 11-month-old boy is brought to the office due to irregular jerking movements. His mother states that for 2 weeks he has looked pale and tired, and he has been more fussy and less playful than usual. Temperature is 36.7 C (98 F), blood pressure is 100/60 mm Hg, pulse is 114/min, and respirations are 16/min. Physical examination reveals spontaneous bursts of nonrhythmic conjugate eye movements in various directions. The patient also has myoclonus involving the trunk and limbs as well as generalized hypotonia. A right-sided, nontender, immobile abdominal mass is palpated. There is no hepatosplenomegaly, and bowel sounds are normal. Complete blood count reveals anemia, and urine is positive for elevated levels of catecholamine breakdown products. Which of the following is the most likely diagnosis?

Question

An 11-month-old boy is brought to the office due to irregular jerking movements.  His mother states that for 2 weeks he has looked pale and tired, and he has been more fussy and less playful than usual.  Temperature is 36.7 C (98 F), blood pressure is 100/60 mm Hg, pulse is 114/min, and respirations are 16/min.  Physical examination reveals spontaneous bursts of nonrhythmic conjugate eye movements in various directions.  The patient also has myoclonus involving the trunk and limbs as well as generalized hypotonia.  A right-sided, nontender, immobile abdominal mass is palpated.  There is no hepatosplenomegaly, and bowel sounds are normal.  Complete blood count reveals anemia, and urine is positive for elevated levels of catecholamine breakdown products.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_39d5_6368_9249_b77bd833d97a_MD0001_00 Nonrhythmic conjugate eye movements and involuntary jerking movements of the trunk and limbs (opsoclonus-myoclonus syndrome) in a young patient should prompt evaluation for neuroblastoma. This is the most common extracranial solid neoplasm of childhood and arises from neural crest cells of the adrenal medulla or sympathetic ganglia. Patients typically present at age <2 with a firm abdominal mass, most often involving the adrenal gland, and constitutional symptoms (eg, weight loss, fatigue). Bone marrow infiltration can cause anemia or pancytopenia, and orbital metastases may result in proptosis and/or periorbital ecchymoses. Although rare, opsoclonus-myoclonus is a paraneoplastic syndrome highly associated with neuroblastoma and is believed to be an autoantibody response to central nervous system antigens. The majority of patients with neuroblastoma have elevated catecholamine metabolites (eg, HVA, VMA) due to the neural crest origin. Biopsy of the mass is diagnostic and will reveal small round blue cells and Homer Wright rosettes. Tumor tissue is subsequently tested for N-myc amplification, which predicts a poor prognosis. (Choice A) Carcinoid tumor is a neuroendocrine tumor that is rare in children. Tumor secretion of serotonin causes carcinoid syndrome (eg, flushing, diarrhea, bronchospasm) and increased 5-hydroxyindoleacetic acid (serotonin metabolite) in the urine. (Choice B) Ewing sarcoma is a malignant bone tumor that arises predominantly in long bones. This neoplasm typically presents in older children and teenagers with pain and swelling over the mass. (Choice C) Medulloblastoma is the most common malignant brain tumor in children. It arises in the cerebellum and causes ataxia, not opsoclonus-myoclonus. As in neuroblastoma, Homer Wright rosettes may be identified; however, urine catecholamine metabolites would not be present. (Choice E) Non-Hodgkin lymphoma can present as an abdominal mass but is rare in infants and not associated with opsoclonus-myoclonus or increased urine catecholamines. (Choice F) Pheochromocytoma is an adrenal tumor that also secretes catecholamines; however, this neoplasm occurs more commonly in adults and is not associated with opsoclonus-myoclonus. (Choice G) Wilms tumor is a renal cancer that presents in early childhood (median age 3-4) with an abdominal/flank mass. In contrast to neuroblastoma, Wilms tumor does not cause opsoclonus-myoclonus or result in catecholamines in the urine. Educational 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. __________ References: Neuroblastoma presenting as opsoclonus-myoclonus: a series of six cases and review of literature. (http://www.ncbi.nlm.nih.gov/pubmed/28217170)

An 11-Month-Old Boy Is Brought to the Office Due to Irregular