Osteolytic lesions and osteoporosis are among the principál causes of morbidity in multiple myeloma (MM). CD56 (NCAM - neuronal cell adhesion molecule) is a molecule that has a role in interactions among cells and between cells and extracellular matrix. The objective of ťhis study was to evaluate the correlations between the expression of CD56, bone disease, and selected biochemical and clinical parameters in MM. The study included 35 patients with newly diagnosed MM and 12 patients with relapse or progression of the disease. The expression of CD56 was detected in bone marrow biopsies using a monoclonal antibody. Malignant plasma cells expressed CD56 in 74.5 % of the patients. No statistically significant differences in selected biochemical markers (beta2-microglobulin, calcium, albumin), bone marrow infiltration, age, gender, myeloma type and stage (Durie-Salmon and IPI) háve been found between the CD56+ and CD56- groups. The expression of CD56 correlated significantly with the presence of osteolytic lesions detected by x-rays (p=0.0006) and with the occurrence of bone events (pathologic fracture or a bone lesion requiring palliative radiotherapy or surgical intervention) (p=0.0339). Thus, CD56 is a useful marker that dosely correlates with the presence of bone disease in patients with MM. In contrast to standard imaging, the expression of CD56 is related to certain intrinsic properties of malignant plasmocytes and, therefore, can predict the clinical course of myeloma bone disease.

        Key words: multiple myeloma, CD56, NCAM, osteolytic lesions