Biochemical properties of blood cells from histiocytosis X patients.

Histiocytosis X (HX) or Langerhans' cell histiocytosis (LCH) is a rare disease, affecting mainly children, in which an abnormal proliferation of Histiocytosis X cells takes place as a result of a primary disorder of the mononuclear phagocyte system [I]. The spontaneous resolution of most cases has led LCH to be regarded as a disorder of the immune regulation rather than a neoplastic process [2]. Although the pathogenesis of LCH is not fully established, the presence of immune defects involving mainly monocytes and lymphocytes has been observed in patients with LCH [3], thus making investigation of such cells from LCH patients worthwhile.