A 24-year-old woman presents with an earache of 4 days in duration. She also reports increased urine production, a skin rash, and bone pain on her scalp. Physical examination reveals otitis media, dermatitis, and exophthalmos. An X-ray of the scalp shows calvarial bone defects. A fine-needle aspirate displays numerous eosinophils. Which of the following is the most likely diagnosis?

LCH refers to a spectrum of uncommon proliferative disorders of Langerhans cells. The disease ranges from asymptomatic involvement of a single site, such as bone or lymph nodes, to an aggressive systemic disorder that involves multiple organs. There is clinical heterogeneity of LCH; eosinophilic granuloma (75% of all cases) is a localized, usually self-limited disorder of older children and young adults; Hand-Schuller-Christian disease is a multifocal and typically indolent disorder, usually in children between 2 and 5 years of age; and Letterer-Siwe disease (fewer than 10% of cases) is an acute, disseminated variant of LCH in infants and children younger than 2 years of age. Organs involved by LCH include the skin (seborrheic or eczematoid dermatitis), lymph nodes, spleen, liver, lungs, and bone marrow. Otitis media is a common finding. Painful lytic lesions of bone are common. Proptosis may complicate infiltration of the orbit. The classic triad of diabetes insipidus, proptosis, and defects in membranous bones characterizes Hand-Schuller-Christian disease. Hodgkin lymphoma (choice A) often features eosinophils but does not have this clinical presentation.Diagnosis: Langerhans cell histiocytosis