<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 4-year-old African-American girl is brought to the physician because of multiple episodes of bilateral leg pain for 4 months. The pain is crampy in nature, lasts up to an hour, and occurs primarily before her bedtime. Occasionally, she has woken up crying because of severe pain. The pain is reduced when her mother massages her legs. She has no pain while attending school or playing. Her mother has rheumatoid arthritis. The patients temperature is 37C 98.6F, pulse is 90min and blood pressure is 9460 mm Hg. Physical examination shows no abnormalities. Her hemoglobin concentration is 12.1 gdL, leukocyte count is 10,900mm3 and platelet count is 230,000mm3. Which of the following is the most appropriate next best step in management?? A: Antinuclear antibody, B: Pramipexole therapy, C: Nafcillin therapy, D: X-ray of the lower extremities, E: Reassurance,  <response>: This is a clinical vignette about a 4-year-old girl with recurrent bilateral leg pain, especially at night. The key findings are episodic crampy leg pain without other symptoms, family history of rheumatoid arthritis, normal vital signs and physical exam. The differential diagnosis includes growing pains, rheumatologic conditions like juvenile idiopathic arthritis, infectious causes, and restless leg syndrome. Imaging the lower extremities would not be useful at this point. Checking an ANA could screen for autoimmune conditions but is premature without more specific findings on exam. Nafcillin would treat infection but there is no evidence for that. Pramipexole treats restless leg syndrome but again is premature without first ruling out more common causes. The best next step is reassurance, as the presentation is most consistent with growing pains, a benign self-limited condition in childhood. E: Reassurance 