A 6-year-old girl arrived...

A 6-year-old girl arrived at the emergency department with a 4-day history of fever, cough, and nasal congestion. She also experiences chronic abdominal pain, described as intermittent periumbilical pain after eating solids, leading to avoidance of solid foods and poor weight gain. Despite extensive investigations, including imaging and endoscopy, no conclusive diagnosis has been reached. Family history includes maternal cutaneous Lupus, leukemia in a cousin, and unclear thyroid diseases in maternal relatives.Suggest a suitable treatment plan and diagnosis??