The natural history of disease in adult Langerhans cell histiocytosis (LCH), with the exception of pulmonary LCH, is unknown. It is unclear whether there are significant differences from childhood LCH, although it appears that multisystem-risk LCH is less aggressive than childhood high-risk disease. The risk of reactivations is unknown.
A group of clinicians experienced in the care of adult LCH patients have published a consensus opinion on the evaluation and treatment of adult LCH patients.
It is estimated that one to two adult cases of LCH occur per million population. The true incidence of this disease is impossible to know because large published studies usually are from referral centers and the disorder often is under-diagnosed. A survey from Germany reported that 66% of the LCH patients were women with an average age of 43.5 years for all patients.
Presentation of adult LCH by organ, site, or system
Adult LCH patients may have symptoms and signs for many months before a definitive diagnosis and treatment. LCH in adults is often similar to that in children, and appears to involve the same organs, although the proportions may be different. There is a predominance of lung disease in adults, usually occurring as single-system disease and closely associated with smoking and with some unique biologic characteristics. An ongoing German registry with 121 registrants showed that 62% had single-organ involvement and 38% had multisystem involvement, while 34% of the total had lung involvement. The median age at diagnosis was 44 years ± 12.8 years. The most common organ involved was lung followed by bone and skin. All organ systems found in childhood LCH were seen, including endocrine and central nervous system, liver, spleen, bone marrow, and gastrointestinal tract. The major difference is the much higher incidence of isolated pulmonary LCH in adults, particularly in young adults who smoke. Other differences appear to be the more frequent involvement of genital and oral mucosa. There may possibly be a difference in the distribution of bone lesions, but both groups suffer reactivations of bone lesions and progression to diabetes insipidus, although the exact incidence is unknown in adults.