A 36-year-old patient presents for painful

swelling on the skull. The swelling seems like a result of some trauma of which

the patient is unaware. At the same time, the swelling has been present for a

long time. An X-ray of the skull is taken and an osteolytic lesion of the skull

bones is discovered under the swelling (such lesion looks like a hole in the

bones and weakens the strength of the bones). This is a so-called eosinophilic

granuloma. Eosinophilic granuloma is a form of Langerhans cell histiocytosis in

adults. It is a monoclonal proliferation of Langerhans cells – special

dendritic cells of the epidermis. Normal Langerhans cells do not divide

further, whereas cell proliferation occurs in Langerhans cell histiocytosis.

Moreover, these cells further migrate to other organs in this disease. Where these cells are normally found in the skin?