Review Question - QID 105590

The boy in this vignette most likely has Langerhans cell histiocytosis (LCH), as evidenced by a solitary, painful, lytic long bone lesion with overlying swelling and hypercalcemia. Langerhans cells are, like macrophages, from the monocytic lineage.

LCH is a family of proliferative disorders of dendritic (Langerhans) which normally function to present antigens to T cells. Classically, dendritic cells have Birbeck granules present on EM ("tennis rackets"). There are several subtypes of LCH including Letterer-Siwe disease (multiple organ involvement including skin, presents in infancy). Hand-Schüller-Christian disease (presents in adolescence with lytic skull lesions, diabetes insipidus, and a scalp rash) and eosinophilic granulomas (no skin involvement).

Schwartz discusses the three histiocytosis X diseases, which are often initially misdiagnosed because of a slow and insidious disease onset. Cutaneous lesions are the most common initial manifestations. Work-up may include a skin biopsy as a rapid and simple means to diagnose histiocytosis X.

Badalian-Very et al. discuss Langerhans cell histiocytosis (LCH) as a category of diseases varying clinical manifestations but with all characterized by proliferating Langerhans cells. Interestingly, LCH's prominent inflammatory component and occasional benign clinical call into question whether LCH is a neoplasm, but other evidence (such as the presence of BRAF mutations) argues against this point.

Image A demonstrates the characteristic Birbeck granules of Langerhans cells which appear as racket-shaped cytoplasmic organelles.

Illustration A shows a "punched out" lesion of the skull (not to be confused with multiple myeloma).

Incorrect Answers:
Answers 1,2,4,5: These cell lineages are not similar to Langerhans cells.