<prompt> A 2 year old child presents with scattered lesions in the skull. Biopsy revealed Langerhans giant cells. The most commonly associated is marker with this candition will beCD 1aCD 57CD 3CD 68  <response>: In Langerhans cell histiocytosis,the hallmark feature is the presence of Birbeck granules on electron microscopy and positivity for S-100 protein and CD 1a. Reference:Essential pediatrics-Ghai,8th edition,page no:620. 