<prompt> An eight year old boy presents with back pain and mild fever. His plain X-ray of the dorsolumbar spine reveals a solitary collapsed dorsal vertebra with preserved disc spaces. There was no associated soft tissue shadow. The most likely diagnosis is -Ewings sarcomaTuberculosisHistiocytosisMetastasis  <response>: Solitary collapsed vertebra vertebra plana with preserved disc spaces in a child suggests the diagnosis of Eosinophilic granuloma a type of Histiocytosis. 