<unk>  (ECD) is an extremely rare disease characterized by the abnormal multiplication of a specific type of white blood cells called histiocytes, or tissue macrophages (technically, this disease is termed a non-Langerhans-cell histiocytosis). It was declared a histiocytic neoplasm by the World Health Organization in 2016. Onset typically is in middle age. The disease involves an infiltration of lipid-laden macrophages, multinucleated giant cells, an inflammatory infiltrate of lymphocytes and histiocytes in the bone marrow, and a generalized sclerosis of the long bones.
Erdheim–Chester disease
Winchester syndrome
Copenhagen disease
Juvenile idiopathic arthritis
Calcium pyrophosphate dihydrate crystal deposition disease
Rheumatoid nodulosis
Secondary systemic amyloidosis
Reactive arthritis