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The disorders of xanthohistiocytic proliferation involving histiocytes, foam cells, and mixed inflammatory cells are divided into Langerhans cell histiocytosis (LCH) and non-Langerhans cell histiocytosis (non-LCH).

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Langerhans Cell Histiocytosis (Histiocytosis X)

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LCH is an idiopathic spectrum of disorders characterized by a clonal proliferation of Langerhans cells. Clinically, LCH is characterized by lytic bony lesions and cutaneous findings that range from soft tissue swelling to eczema- and seborrheic dermatitis-like skin changes and ulceration.

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Insight

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Histiocytosis can be extremely difficult to diagnose. In infants with diaper rash that will not heal, particularly if there are erosions in the folds or petechiae/purpura, histiocytosis should be considered.

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Synonyms Class I histiocytosis, nonlipid reticuloendotheliosis, eosinophilic granulomatosis.

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Classification

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LCH has four overlapping forms:

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  1. 1. Letterer–Siwe disease: aggressive LCH with diffuse skin and organ infiltration and thrombocytopenia

    2. Hand-Schüller-Christian disease: LCH with lytic skull lesions, exophthalmos, and diabetes insipidus

    3. Eosinophilic granuloma: single osteolytic bony lesion ± skin/soft tissue lesion

    4. Hashimoto–Pritzker disease: congenital self-healing reticulohistiocytosis

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Epidemiology

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Age Any age, common 1 to 3 years.

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Gender M > F, 2:1.

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Incidence Rare, 5/million children.

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Genetics Familial case reports.

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Pathophysiology

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The proliferating Langerhans cell appears to be primarily responsible for the clinical manifestation of LCH. The stimulus for the proliferation may be a disturbance of intracellular lipid metabolism, a reactive response to infection (?viral), a primary immunologic disorder of the host, or an inherited neoplastic disorder.

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History

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LCH has a broad clinical spectrum, but in the most aggressive form (Letterer–Siwe disease), the infant appears systemically ill with a generalized skin eruption (seborrhea, petechiae, and purpura) followed by fever, anemia, thrombocytopenia, adenopathy, hepatosplenomegaly, and/or skeletal lesions.

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Physical Examination

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Skin Findings
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Type Papules, plaques, vesicles, scale, petechiae, purpura, ulceration, necrosis.

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Color Pink, flesh-colored.

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Size 1 to 2 mm.

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Distribution Flexural areas: neck, axillae (Fig. 19-1), and perineum > trunk (Fig. 19-2).

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FIGURE 19-1
Graphic Jump Location

Histiocytosis X Erythematous plaques with ulceration and maceration in the axilla of an infant.

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FIGURE 19-2
Graphic Jump Location

Langerhans cell histiocytosis Erythematous papules and a crusted, purpuric plaque on the abdomen of an infant.

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General Findings
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Fever Lymphadenopathy (LAD). Ill appearance.

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Pulmonary Infiltrate disease of the lung bases and midzones, pneumothorax.

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Liver Hepatosplenomegaly.

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Bone Osteolytic lesions: calvarium, sphenoid bone, sella turcica, mandible, long bones of upper extremities (UEs), vertebrae.

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