Treatment of Langerhans Cell Histiocytosis (LCH)

Disease Classification and Diagnosis

The American Thoracic Society recommends disease classification, which includes single-system single-site (SS-s) and single-system multiple-site (SS-m) 2
Diagnosis of LCH requires histopathologic confirmation with immunohistochemical staining (CD163/CD68, S100, CD1a, Langerin), as recommended by the Mayo Clinic 3
High-resolution CT for pulmonary involvement is necessary, showing characteristic peribronchiolar nodular infiltrates with cystic spaces, according to Praxis Medical Insights 1
Bronchoalveolar lavage (diagnostic if CD1a-stained cells exceed 5%) is also recommended by Praxis Medical Insights 1

The American College of Chest Physicians recommends smoking cessation as the cornerstone for pulmonary LCH, which may result in clinical improvement in approximately 33% of patients 1
For symptomatic or progressive disease, systemic corticosteroids and vinblastine are recommended, as suggested by the American Thoracic Society 2
Targeted therapies, such as BRAF inhibitors (e.g., vemurafenib), are recommended for BRAF V600E-mutant disease, as approved by the FDA and reported by the Mayo Clinic 3, 4
For refractory disease, cytosine arabinoside (cytarabine) and cladribine may be considered, according to the American Thoracic Society 2

The American College of Chest Physicians recommends first response assessment within 4 months of initiating treatment, with surveillance intervals extended to 6-12 months if disease stabilizes or enters remission 1

The mortality rate is approximately 10% in patients with progressive pulmonary disease, as reported by Praxis Medical Insights 1
Targeted therapies directed at the MAPK/ERK pathway mutations present in >90% of LCH patients may improve prognosis, as reported by the Mayo Clinic 4