[Characteristics of long-term complications in Langerhans cell histiocytosis]

About 100 cases of Langerhans cell histiocytosis (LCH) occur annually in Japan. It predominantly occurs in infants, presenting as multisystem disease or multifocal bone involvement. However, LCH can also occur in adults aged 20 to 40. Single-system skin involvement is rare, with most cases presenting with multisystem disease, including bone lesions, which respond to chemotherapy. In adults, lung lesions that improve with smoking cessation are well-known, although multisystem disease is more common and requires aggressive therapeutic intervention similar to that in children. In some infant cases, progression of liver, spleen, and bone marrow lesions can be difficult to control and can become severe. However, targeted molecular therapies are now available as a lifesaving option. More than 30% of cases of multisystem LCH recur at least once, often leading to long-term complications. In particular, the emergence of central diabetes insipidus, anterior pituitary dysfunction, and central nervous system neurodegenerative disorders several years after the diagnosis of LCH is a unique feature not observed in other diseases. New therapeutic strategies are needed to counter these problems.