Overview Flashcards
What is Langerhans cell histiocytosis (LCH)?
A rare disorder characterized by single or multiple osteolytic bone lesions demonstrating infiltration with histiocytes. These histiocytes (which is an antiquated term referring to WBCs that reside in tissue throughout the body), along with lymphocytes, macrophages, and eosinophils may infiltrate nearly every organ. LCH is characterized by an uncontrolled clonal proliferation of Langerhans cells which belong to the normal human mononuclear-phagocytic system.
Is there a sex predilection in LCH? What is the estimated annual incidence in the United States?
Yes. Males are more commonly affected than females (3:2). ∼1,200 cases/yr of LCH in the United States. It is likely underdiagnosed in the general population. It is most common in children 1–3 yrs.
What is the cell of origin of LCH?
LCH results from dysregulated differentiation program of myeloid dendritic cell precursors (and notfrom epidermal dendritic cells called Langerhans cells). As a result, it has been suggested that LCH (along with juvenile xanthogranuloma and Erdheim–Chester Dz) be reclassified as inflammatory myeloid neoplasms. (Berres M et al., Adv Immunol 2013)
What are the diagnostic histopathologic characteristics of LCH?
Pathologic findings vary depending on the site of the Bx, but is confirmed by immunohistochemistry demonstrating the presence of dendritic cell markers such as CD1a, S100, and CD207 (Langerin).
What is the normal function of Langerhans cells? Where are they normally found?
Langerhans cells serve as antigen presenting cells to lymphocytes and are typically found in skin, mucosa, spleen, and lymphatics.
What organs are typically involved in LCH?
Bones (children) and lungs (adults), but LCH can present in any organ (e.g., liver, skin, etc.). LCH is limited to 1 organ system (e.g., bone) in 55% of cases and skin involvement is seen in 40% of cases.
How does LCH relate to other histiocytosis entities like eosinophilic granuloma, Letterer–Siwe Dz, Hand–Schuller–Christian Dz, and histiocytosis X?
All are antiquated terms. Eosinophilic granuloma is an older term for focal LCH, while the eponyms represent multifocal Dz. Histiocytosis X is the older term for LCH in general.
In what age group are widespread seborrheic rashes in the scalp/groin, +LAD, and liver involvement seen with LCH?
These Sx are seen in LCH pts <2 yo.
For what age group is DI a common presentation of LCH?
>2 yo (20%–50%). In this group, bone (pain +/– ST mass), lung, oral mucous membrane, and cerebral involvement by LCH can be seen.
What age group and sex predominance is seen in LCH?
Male predominance (56%-66% of patients). About 50% of cases are diagnosed between ages 1 and 15.
