Spontaneous remission of multi-system histiocytosis X.

Two infants presented with biopsy-proven histiocytosis X affecting multiple sites. Since neither showed evidence of organ failure or of constitutional upset, no specific therapy was given. In each case there was long-lasting spontaneous regression of disease. Analysis of blood mononuclear cells revealed a raised T4:T8 (helper:suppressor T lymphocyte) ratio at diagnosis but a normal ratio during remission. These observations support the argument that multi-system histiocytosis X, even in infants (Letterer-Siwe disease), is not a malignancy and that an "expectant" treatment policy may be indicated in selected patients.