Letterer–Siwe disease is one of the four recognized clinical syndromes of Langerhans cell histiocytosis (LCH). It causes approximately 10% of LCH disease and is the most severe form. Prevalence is estimated at 1:500,000 and the disease almost exclusively occurs in children less than three years old. Clinical presentation: 1. Skin lesions 2. Hepatosplenomegaly 3. Lymphadenopathy 4. Lung lesions 5. Osteolytic lesions 6. Pancytopenia 7. Ear drainage