<prompt> Langerhans cell histiocytosis true is all except ?Peak incidence less than 3 years of ageRadiosensitiveDiffuse form is known as litter-sewe-diseaseGonadal involvement occurs  <response>: Ans. is d i.e., Gonadal involvement occurs Peak incidence of langerhans cell histiocytosis is seen in children less than 5 years. o Multifocal, multisystem langerhans cell histiocytosis is known as letter-sewe disease. o Low dose radiotherapy is effective in single system disease. Also know Childhood histiocvtosis o Three classes of childhood histiocytosis are recognized based on histopathological findings Now histiocytosis is classified into :- i Histiocytosis I ii Histiocytosis II iii Histiocytosis III o The most well known childhood histiocytosis previously known as histiocytosis X constitutes class I histiocytosis and includes the following three :? o Letterer - Siwe disease Acute fielminant disseminated disease o Eosinophilic granuloma Solitary or few indolent lesions of bone o Hand schuller christian disease Intermediate form characterized by multifocal chronic involvement and classically presents as triad of diabetes insipidus proptosis and lytic bone lesin o Class I histiocytosis is also known as langherhans cell histiocytosis. 