Rapidly progressive myopathy: unveiling light chain amyloidosis as an initial manifestation of multiple myeloma: a case report and literature review.

We present the case of a 79-year-old man with rapidly progressive myopathy as the initial manifestation of light chain amyloidosis associated with multiple myeloma. The patient experienced progressive lower limb weakness resulting in difficulty climbing stairs. Ancillary tests revealed slightly elevated serum creatine kinase levels. The electromyogram revealed a diffuse myogenic pattern while muscle MRI indicated fatty replacement of the quadriceps muscles. Muscle biopsy revealed the presence of amyloid deposits in the vessel walls. An elevated level of lambda (246 mg/L) light chain was detected. The bone marrow aspiration results were consistent with the diagnosis of multiple myeloma. In conclusion, even if amyloid myopathy is a rare condition, routine screening for amyloid deposits in muscle biopsy is crucial and should be performed systematically. In the present case, it enabled a rapid diagnosis and the beginning of treatment.

RelA and RelB cross-talk and function in Epstein-Barr virus transformed B cells.

In this study, we determined the respective roles of RelA and RelB NF-κB subunits in Epstein-Barr virus (EBV)-transformed B cells. Using different EBV-immortalized B-cell models, we showed that only RelA activation increased both survival and cell growth. RelB activity was induced secondarily to RelA activation and repressed RelA DNA binding by trapping the p50 subunit. Reciprocally, RelA activation repressed RelB activity by increasing expression of its inhibitor p100. To search for such reciprocal inhibition at the transcriptional level, we studied gene expression profiles of our RelA and RelB regulatable cellular models. Ten RelA-induced genes and one RelB-regulated gene, ARNTL2, were repressed by RelB and RelA, respectively. Apart from this gene, RelB signature was included in that of RelA Functional groups of RelA-regulated genes were for control of energy metabolism, genetic instability, protection against apoptosis, cell cycle and immune response. Additional functions coregulated by RelA and/or RelB were autophagy and plasma cell differentiation. Altogether, these results demonstrate a cross-inhibition between RelA and RelB and suggest that, in fine, RelB was subordinated to RelA. In the view of future drug development, RelA appeared to be pivotal in both classical and alternative activation pathways, at least in EBV-transformed B cells.