DISEASES OF HISTIOCYTES AND DENDRITIC CELLS
Langerhans histiocytosis is common in children. It can affect many sites, including skin, bone, CNS (diabetes insipidus), and lungs. Biopsy is required for diagnosis. The Langerhans cells are CD1a positive and on electron microscopy show cytoplasmic Birbeck granules (tennis racket–shaped organelles).
• Multisystem variant: Letterer-Siwe disease (marrow involvement can be fatal)
• Hand-Schuller-Christian triad is calvarial involvement, diabetes insipidus, and exophthalmos
• Unisystem variant: eosinophilic granuloma (most often found in bone)