Erdheim-Chester disease diagnosed by 99m Tc-MDP bone scintigraphy and brief literature review.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis with lipid-laden macrophages and fibrosis. Although ECD is a multisystemic disease, the most common finding is sclerotic bone involvement in the diametaphyseal regions of bilateral distal femur and in proximal and distal tibia. We present a 40 years old woman who for the last two years had various systemic symptoms, especially knee pain, polyuria and polydipsia. Although a "hot knee" pattern was seen in bone scintigraphy (BS), a femur biopsy was performed, due to the preliminary diagnosis of haematologic malignancy. The biopsy specimen showed only intense fibrosis. One year later while the patient was in our clinic, BS showed characteristic for ECD bone involvement. Bone biopsy specimens stained in hematoxylin and eosin showed dense fibrosis but not histiocytosis. However, after immunohistochemical staining with CD-68, histiocytes were discerned. In conclusion, the authors underline that ECD was diagnosed at a second diagnostic attempt both clinically and by specific staining pathology specimens.