Potential relationship between MuSK-MG and autologous hematopoietic stem cell transplantation: a case report

A 61-year-old woman developed anti-muscle-specific tyrosine kinase antibody positive myasthenia gravis (MuSK-MG) three years after autologous hematopoietic stem cell transplantation (HSCT) for multiple myeloma. Symptoms improved following methylprednisolone pulse therapy, intravenous immunoglobulin, plasma exchange, and the addition of efgartigimod. A review of the literature revealed that all four previously reported cases of myasthenia gravis after autologous HSCT were MuSK-MG, although none were positive for anti-acetylcholine receptor (AChR) antibodies. This frequency differs significantly from the reported incidence of MuSK-MG in the general population and in patients following allogeneic HSCT, suggesting a potential association between autologous HSCT and MuSK-MG. Hypothesized mechanisms include a paraneoplastic mechanism and changes of IgG4 production following immune reconstitution after autologous HSCT. We suggest that clinicians should be aware of this possibility and consider MuSK-MG in the differential diagnosis of neurological symptoms that arise after autologous HSCT, even though autologous HSCT can be used as a therapeutic option for MuSK-MG.