Different manifestations of langerhans cell histiocytosis affecting two members of a family.

Two different manifestations of Langerhans cell histiocytosis (histiocytosis X) are presented, the first occurring as a solitary rib eosinophil granuloma in an 11-year-old girl, and the second as an eosinophil granuloma of the lung of her mother, a 41-year-old heavy smoker, appearing 8 years after the onset of her daughter's disease. Familial clustering of two different manifestations of histiocytosis X disease is very rare and raises the possibility of inherited mutations that promote emergence of clonal Langerhans cells.