Favourable prognostic features in histiocytosis X: bone involvement and absence of skin disease.

The records of 70 patients presenting to this hospital since 1961 with histiocytosis X confirmed by biopsy examination have been reviewed. The patients were subdivided into three groups: group A, those under 2 years of age at diagnosis; group B, those between 2 and 5 years; and group C, those over 5 years. All eight patients who died (11% overall mortality) were under 2 years of age at diagnosis. Involvement of lung, liver, and bone marrow were confirmed as poor prognostic features. The presence of bone disease and absence of skin rash were identified as favourable features.