DISCUSSION
In the cases reported in the literature, there is a high rate of hematological and clinical responses to ASCT treatment with some patients responding only to the second ASCT[13, 28]. The clinical case we present initiated treatment 14 months after disease onset and did not achieve a good response after ASCT, showing some intensification of the myopathy after transplant followed by a stabilization and later slight improvement in autonomy in the daily life activities.
The most significant revision of transplanted SLONM-MGUS patients identified, as predictors of inadequate response to ASCT, the long course of the disease before the hematological treatment and the persistence of gammopathy after treatment[28], which were present in our clinical case. Furthermore, the increase of the M protein level precedes clinical deterioration, and there is a correlation between clinical course and amount of protein detected in peripheral blood[11, 28]. Age at onset, light chain type of the monoclonal protein (kappa vs lambda) and severity of muscle weakness are not associated with a specific outcome[28].
Delayed ASCT may have affected response to treatment. However, according to these data which suggests a correlation between clinical course and gammopathy response, the goal of treatment should always be a complete response with suppression of the neoplastic clone, as soon as possible, to reduce the monoclonal protein and its toxic effects. Efficacy of Chemotherapy toward plasma cell dyscrasia without stem-cell transplantation has been reported as well[13]. In order to deepen hematological response to achieve a parallel clinical improvement, patients should receive additional Chemotherapy targeting plasma cell clone. Our clinical case illustrates the importance of implementing several treatments, such as proteasome inhibitors and immunomodulators, to obtain a complete hematologic response and consequently, the best clinical improvement. The complete hematologic response was achieved with the third line of treatment, allowing stabilization of muscle weakness and an impressive recovery of body weight. This approach supports the rationale of treating the monoclonal gammopathy to get the best neurological symptoms response [19, 20, 26, 28]. Whether or not nemaline rods diminished in our patient with treatment is not known, as a muscle biopsy was not performed after clinical improvement.
This clinical case shows that proteasome inhibitors and immunomodulators might be an effective therapy of SLONM related to monoclonal gammopathy in cases without a good response to ASCT or for patients with comorbidities who are not eligible for ASCT.
Even though the nature of the relationship between SLONM and monoclonal gammopathy is not entirely clarified, the correlation between clinical response and hematological response suggests a direct association between M protein and the disorder[13, 14]. All of these data have transformed SLONM associated with monoclonal gammopathy in a treatable disease with therapy directed toward plasma cell dyscrasia rather than immunosuppressive drugs used in autoimmune diseases[14]. The goal to eradicate clonal plasma cells, similar to other plasma cell dyscrasias makes logical the proposition to classify SLONM associated with monoclonal gammopathy as a monoclonal gammopathy with neurological significance (MGNS) and as a plasma cell dyscrasia with toxic monoclonal protein, similar to AL amyloidosis or POEMS [13, 28].