<prompt> Least common cause of pericarditispericardial effusion in children:Rheumatic feverSarcoidosisRheumatoid arthritisSLE  <response>: b. SarcoidosisRef: Nelsons 20e p 2269-2271, Ghai 8e p 433-443Important causes of pericarditispericardial effusion in children:Infectious Viral Coxsackie virus B, EBV, Influenza, Adenovirus; Fungal Histoplasmosis, Actinomycosis Bacterial TB, Streptococcus, Pneumococcus, Staphylococcus, Meningococcus, Mycoplasma, Tularemia, Listeria, Leptospirosis Immune complex Meningococcus, Hemophilus influenzae Parasitic Toxoplasmosis, Echinococcosis Connective tissue diseasesMetabolic-endocrineRheumatoid arthritisRheumatic feverSystemic lupus erythematosusSystemic sclerosisSarcoidosisWegener granulomatosisUremiaHypothyroidismChylopericardiumOut of the causes given in the options, Sarcoidosis is the least common. 