Histiocytosis

CHAPTER 23 Histiocytosis

Mohannad Ibrahim

Epidemiology

Langerhans cell histiocytosis (LCH) is a rare disease with an incidence of 0.2 to 2.0 cases per 100,000 children under 15 years of age. It comprises a wide spectrum of clinical manifestations associated with the proliferation of Langerhans cells. The term was adopted by the Philadelphia Workshop of the Histiocyte Society to identify a group of diseases previously known as eosinophilic granuloma of bone, Hand-Schüller-Christian disease, and Letterer-Siwe disease. LCH may present as isolated osseous involvement (36%), isolated nonosseous involvement (33%), or multisystem involvement. It can be unifocal (65%) or multifocal (35%). Bony involvement is the most frequent, with estimated 15 to 61% of the patients having otologic involvement, with bilateral temporal involvement seen in 30% of the patients. Children with otologic involvement have a higher risk of poor response and higher percentage of second line treatment.

Clinical Features

Langerhans cell histiocytosis usually presents in the first decade. There is an inverse relationship between age of presentation and severity of disease, with Letterer-Siwe disease present in the first 3 years, Hand-Schüller-Christian present between 3 and 5 years, and unifocal LCH (eosinophilic granuloma) present between 5 and 20 years. Otologic involvement is usually seen in younger age groups and is more frequently seen in multisystemic disease. It can be the initial presentation in 5 to 25% of patients. Patients with temporal bone involvement can infrequently be asymptomatic; however, patients are commonly symptomatic and usually present with chronic otorrhea, mastoiditis, external auditory canal lesions, otitis, and conductive or sensorineural hearing loss. Diagnostic errors are frequent because the otologic findings are similar to those of other conditions, particularly otomastoiditis.

Pathology

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