[Utility of 8-colours multiparameter flow cytometry immunophenotyping of plasma cells for the management of monoclonal gammopathy]. / Intérêt de la cytométrie en flux multiparamétrique 8 couleurs dans la prise en charge des gammapathies monoclonales.

Bone marrow flow cytometric analysis is a powerful and rapid tool for evaluating aberrant plasma cell. In this study, we have examined the utility of multiparameter flow cytometry (MFC) in 52 patients with multiple myeloma (MM) and in 45 patients with monoclonal gammopathy with unknown significance (MGUS) into routine evaluation for the management of patients with plasma cell-related disorders. The plasma cells (PC) were identified by their light scatter distribution and reactivity patterns to CD138, CD38, and CD45. The combination of these parameters was helpful for identifying distinct subpopulations of PCs. Moderate to bright expression of CD56, CD20, CD24, CD28, and CD117 was detected in 67%, 26%, 13%, 27%, and 57% of MM cases and in 58%, 20%, 11%, 43% and 44% of MGUS cases, respectively. In MGUS group, the median percentage abnormal PCs/total PCs was 88% with 37 patients out of 45 (82%) with ratio <95%. The median ratio of the MM group was 98.9% and a ratio ≥ 95% was observed in 37 samples out of 44 (84%). In conclusion, MFC immunophenotyping of PCs has obvious clinical relevance in differential diagnosis between MM and others monoclonal gammopathies, identification of high-risk MGUS and smouldering MM, and minimal residual disease monitoring of MM. Our results showed that this tool can be easily applied in haematology laboratories.

First case of human spondylodiscitis due to Shewanella algae.

We present the first case of human spondylodiscitis due to Shewanella algae. Our patient did not have any predisposing factors. The portal of entry was probably a cutaneous lesion on the leg, exposed to seawater. Bacteria were isolated in pure culture from a needle biopsy specimen of the vertebral disk. Automated identification systems identified the organism as Shewanella putrefaciens. However, molecular biology identified it as S. algae. Treatment with ceftriaxone and amikacin, then ciprofloxacin successfully addressed the infection. We also review four published cases of human osteoarticular infections caused by Shewanella spp: two cases of arthritis and two cases of osteomyelitis. Two patients had predisposing factors, and contact with water was found in two cases. The clinical, radiological and biological characteristics of S. algae spondylodiscitis are indistinguishable from those of spondylodiscitis of other causes. A cutaneous lesion with exposure to water is a potential portal of entry. Molecular typing is necessary to obtain a precise bacteriological identification.

Multiple myeloma cells directly stimulate bone resorption in vitro by down-regulating mature osteoclast apoptosis.

Multiple myeloma (MM) is characterized by devastating bone destruction mainly due to stimulation of osteoclastogenesis. However, whether MM cells can directly influence osteoclast apoptosis, a mechanism that would contribute to increase the number of active osteoclasts, has not been addressed yet. Herein, using authentic mature rabbit osteoclasts, we demonstrated that conditioned media (CM) prepared from U266 and RPMI8226 cells but not from LP-1 and OPM-2 cells, stimulated bone resorption and inhibited osteoclast apoptosis in a dose-dependent manner. The MM cells which exerted an anti-apoptotic effect secreted high amounts of M-CSF and addition of a neutralizing antibody against M-CSF reversed the CM effects. Imatinib mesylate, a tyrosine kinase inhibitor that can target the M-CSF receptor, also prevented the effect of CM. These findings suggest that M-CSF originating from MM cells may play a critical role in MM bone disease by decreasing osteoclast apoptosis.