Group of disorders that have in common, as a primary event, the accumulation and infiltration of histiocytes, monocytes, macrophages, and dendritic cells in the affected tissues. It involves mainly the skin, bones, brain, lungs, spleen, and liver. It is often characterized by the presence of nonmalignant growths as a result of accumulation of histiocytes. This is associated with a very poor prognosis (70% mortality).
Langerhans Cell Histiocytosis; LCH; Reticulogranulomatosis; Histiocytosis X.
Estimated annual incidence ranges from 0.5 to 5.4:1,000,000 persons per year, but this probably is underestimated. Male-to-female ratio is 2:1. According to the Histiocytosis Association of America (HAA), 1 in 200,000 children in the United States are born with histiocytosis each year. HAA also states that most of the people diagnosed with histiocytosis are children under the age of 10, although the disease can afflict adults. The University of California, San Francisco, states that the disease usually occurs from birth to age 15.
Consanguinity has been reported.
LCH could arise secondary to a somatic mutation of a gene with clonal proliferation of the specific cells as a consequence. LCH cells synthesize various cytokines, including interleukin (IL)-1, tumor necrosis factor-α, and granulocyte-macrophage colony-stimulating factor (GM-CSF), which can explain certain systemic signs of the disease.
Clinically evocated and confirmed by laboratory investigations. Different levels of probability have been described for the diagnosis:
Presumed: Light morphologic characteristics
Probable: Light morphologic features plus two or more supplemental positive stains for the following: adenosinetriphosphatase, S-100, α-d-mannosidase protein, and peanut lectin
Definitive: Light morphologic characteristics plus Birbeck granules in the lesional cell (electron microscopy) and/or staining positive for CD1a antigen (T6) on the lesional cell
Because of the dissemination of the disease, clinical signs are multiple and can involve a large part of the body.
Bones (78%): Typical punched-out cavity. Lesions can be asymptomatic or revealed by pathologic fracture or regional complications (loss of teeth, pain, periosteal inflammation). Most frequently involved bones are skull (49%), innominate bone 23%, femur 17%, orbit 11%, and ribs 8%.
Skin (50%): Lesions occur during the first months of life. Rash is frequent. Bronzing of the skin can occur. Infiltrates (maculoerythematous, petechial xanthomatous, nodular papula) have a predilection for the midline of the trunk and the peripheral and flexural areas of skin. Scalp lesion can lead to alopecia. There is no pruritus.
Chest (20-40%): Interstitial syndrome (nodular images) caused by a restrictive syndrome with clinical manifestations such as cough tachypnea and dyspnea. Diagnosis is based on bronchoalveolar washing. Pulmonary fibrosis and pneumothorax can occur.
Digestive System: Relatively rare, ranging ...