A Rare Case of Erdheim-Chester Disease and Langerhans Cell Histiocytosis Overlap Syndrome

Table 1

Pertinent differences between the two varieties of histiocytic disorders.

Clinical and immunohistochemical features	Histiocytosis
	Langerhans’ cell	Non-Langerhans’ cell
Incidence	Higher	Lower
Mortality	Lower (10%)	Higher (57%)
Culprit cells	Langerhans’ cells	Foamy macrophages
Culprit lineage	Langerhans-dendritic cell lineage	Monocyte-macrophage lineage
CD 68	+	+
CD 1a	+	−
S100	+	−
Central nuclear groves	+	−
Birbeck granules	+	−
Age of onset	Children or young adults	The elderly (50s–70s)
Skin involvement	More	Less
Skeletal involvement	Asymmetric osteolytic lesion of skull and flat bones	Symmetric osteosclerotic lesions of long bones
Proliferative index	2–60%	<3%