Definition of Histiocytosis, Letterer Siwe

Histiocytosis, Letterer Siwe: A severe disease in which histiocytes start to multiply and attack the tissues or organs of the patient starting in infancy with a scaly, sometimes itchy rash on the scalp, ears, abdomen, and creases of the neck and face. Raw skin may provide a portal of entry for germs, leading to sepsis (bloodstream infection). There are often draining ears, swollen glands, enlargement of the liver and spleen, liver disease, anemia and neutropenia (low white blood cells). Loss of appetite, irritability, failure to thrive, and respiratory symptoms may occur. Because of their appearance, these children may be misdiagnosed as abused.

Letterer-Siwe disease is the most severe form of Langerhans cell histiocytosis.