[Condensing myeloma. Apropos of 2 cases with bone histomorphometric study].

Two cases of myeloma with roentgenographic evidence of bone sclerosis confirmed by iliac histomorphometric measurements are reported. In one patient, increased resorption, major depression of osteoblast activity, initial intense myelofibrosis, and myeloid deposits were found. The other patient had both increased resorption and increased osteoblast activity with clinical manifestations suggestive of POEMS syndrome. These two cases are compared with 116 cases previously published in the occidental medical literature and with five histomorphometric studies demonstrating increased bone trabecula volume (BTV). Conventional histologic studies suggest several mechanisms as possible explanations for the occurrence of bone sclerosis, including increased modeling unit activity, isolated osteoblast activation, metamorphic neoosteogenesis in myelofibrosis foci, and, in exceptional cases, inhibition of resorption due to increased production of calcitonin. The diversity of bone modeling patterns evidenced by the seven histomorphometric studies reviewed in this article is striking. Bone modeling patterns provide only a snapshot of bone modeling units and may vary over time in a given patient. Reported cases are too few to allow conclusions but emphasize the need for performing further histomorphometric investigations.