Histiocytosis

Histiocytoses constitute a heterogeneous group of rare disorders characterized by the infiltration of almost any organ by myeloid cells with diverse macrophage or dendritic cell phenotypes. These disorders can begin at any age.
Emile et al. 2021 The Lancet 398: 157-170

Diagnosis is based on histology combined with appropriate clinical and radiological findings. Due to the low incidence and broad spectrum of clinical manifestations, there is often a diagnostic delay, especially in adults.
Emile et al. 2021 The Lancet 398: 157-170

In most cases, biopsy specimens infiltrated by histiocytes exhibit somatic mutations in genes that activate the MAP kinase cell-signaling pathway. These mutations might also be present in the blood cells and hematopoietic progenitors of patients with multisystem disease.
Emile et al…