Nonsecretory multiple myeloma with osteoporosis: immunocytologic and bone resorptive studies.

Two patients, ultimately found to have advanced nonsecretory multiple myeloma, presented with skeletal pain, diffuse skeletal demineralization, and fractures. The correct diagnosis was initially obscured by the absence of typical hematologic findings and discrete lytic bone lesions. Bone marrow examination was diagnostic. Intracytoplasmic IgA or IgD kappa was demonstrated in the myeloma cells of each case. Decreased quantitative polyclonal serum immunoglobulins and hypercalcemia were important clinical clues. The demonstration of increased osteoclast activating factor (OAF) derived from the cultured myeloma cells from each case suggests that the secretion of OAF and immunoglobulin are unrelated.