Cutaneous histiocytoses in children

Cutaneous histiocytoses constitute a heterogeneous group of diseases characterised by the cutaneous accumulation of cells with the cytological and phenotypic features of macrophages or dendritic cells. The clinical spectrum ranges from self-resolving, skin-limited conditions to severe, multiorgan disease with a high morbidity rate. Until recently, cutaneous histiocytoses were classified according to the immunophenotype of the pathological cells, with differentiation between Langerhans cell histiocytosis (LCH) [CD1a+, CD207 (langerin)+] and non-Langerhans cell histiocytosis (CD68+, CD163+, CD1a-, CD207-). Over the last 12 years, a number of new pathophysiological findings (in particular, molecular pathology results) regarding histiocytoses have contributed to a new classification based on molecular alterations, as well as on clinical and imaging characteristics and the phenotype. The most frequent entities in children are juvenile xanthogranuloma and LCH.