Abstract

BackgroundThe onset of myasthenia (MG) gravis with anti-muscle-specific tyrosine kinase (MuSK) antibodies most commonly peaks in the fourth decade of life, and MG with MuSK antibodies (MuSK-MG) rarely coexists with a malignant tumor. To date, MuSK-MG has not been reported in multiple myeloma (MM).Case presentationA 60-year-old male with MM who was receiving treatment with bortezomib and thalidomide presented diplopia, ptosis, and limb weakness. A diagnosis of MM with Bence-Jones proteinuria was established when he was 56 years old, and he received chemotherapy with four courses of bortezomib and dexamethasone. Although he received thalidomide as maintenance therapy, it was discontinued a year before hospital admission because of sensory neuropathy as a side effect. Six months before hospital admission, he developed mild diplopia. One month before admission, his chemotherapy was interrupted because of viral infection and fatigability. Then he developed neck weakness and bilateral ptosis. A diagnosis of MuSK-MG was made based on neurological and serological examinations. According to the previous relevant literature, this is the first report of MuSK-MG in a patient with MM.ConclusionsIn patients with MM, the possibility of co-existing of autoimmune disease, including MuSK-MG, should be considered. This case emphasizes the need to still consider testing for anti-MuSK antibodies in older MM patients where there is clinical suspicion for possible MG despite negative anti-acetylcholine receptor antibodies and lacking classic MuSK MG phenotype at onset.

Highlights

  • The onset of myasthenia (MG) gravis with anti-muscle-specific tyrosine kinase (MuSK) antibodies most commonly peaks in the fourth decade of life, and Myasthenia gravis (MG) with MuSK antibodies (MuSK-MG) rarely coexists with a malignant tumor

  • Blot clonality was not observed on immunoelectrophoresis. He had received chemotherapy with bortezomib and dexamethasone, followed by other drugs and agents (Fig. 1). He was treated with thalidomide as maintenance therapy, that was discontinued 1 year before hospital admission because of sensory neuropathy side effects

  • The patient was diagnosed with MG that was categorized according to the Myasthenia Gravis Foundation of America (MGFA) criteria [3] as Class IIa

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Summary

Conclusions

In patients with MM, the possibility of co-existing of autoimmune disease, including MuSK-MG, should be considered.

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