| • | head and neck (but mucous membranes always spared) |
| • | begins first 3 years of life, evolves for several years then resolves spontaneously |
| • | do not develop systemic disease |
| • | electron microscope: comma shaped bodies (“worm shaped”) in cytoplasm of histiocytic infiltrate |
ddx:
| • | JXG, papular xanthoma, urticaria pigmentosa (Darier’s sign) – histology |
| • | generalized eruptive histiocytosis – distinguished by age of onset and distribution |
| • | histiocytosis X (especially chronic disseminated form: Hands-Schuller-Christian) – distribution, immunohistochemistry, EM |
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