Erdheim-Chester disease: a case report with immunohistochemical and biochemical examination.

This report describes a 47-year-old man with Erdheim-Chester disease (EC), the second case reported in Japan. The patient complained of knee pain, and the roentgenogram of the bilateral legs revealed symmetric osteolytic lesions with sclerosis of the metaphyseal regions of the long bones. Histological examination of the biopsy specimen showed a xanthogranulomatous lesion consisting of aggregations of foamy macrophages and Touton-type giant cells. Immunohistochemical study of the foamy cells in the lesion showed positive reaction to anti-Kp-1, anti-S-100 alpha, beta, anti-neuron-specific enolase (NSE), anti-alpha-1-antichymotrypsin, anti-alpha-1-antitrypsin, and anti-lysozyme antibodies. Electron microscopy showed many lipid droplets in the cytoplasm, but no Langerhans granules. These results suggested that the disease was part of the spectrum of histiocytosis but was different from Langerhans cell histiocytosis. Biochemical analysis of material extracted from a lesion showed the predominance of cholesterol ester. The disease progressed to central diabetes insipidus, and the involvement of multiple organs was indicated by a magnetic resonance image.