Muscle‐specific kinase (MuSK) antibody‐associated myasthenia gravis after bone marrow transplantation

Abstract

There have been 20 reported cases of myasthenia gravis (MG) following bone marrow transplantation (BMT) ( Table 1). 1,4,8,10,13,15,16 Acetylcholine receptor antibodies (AchR-ab) were present in 18 cases. We report the first case of BMT-associated MG with antibodies directed against muscle-specific tyrosine kinase (MuSK-ab). CASE REPORTA 54-year-old woman was diagnosed with non-Hodgkin lymphoma in February 2003, she was treated with chemotherapy, and followed by an allogeneic BMT. Since then she has been in remission and has never had graft-versushost disease (GVHD).In March 2006 she developed generalized weakness, diplopia, dysphagia, and an aspiration pneumonia. Following treatment of the pneumonia there was difficulty weaning from the ventilator. Neurological exam revealed ptosis, ophthalmoplegia, and severe proximal weakness. Motor and sensory nerve conduction studies were unremarkable. Needle electromyography revealed short duration, decreased amplitude motor unit potentials. Repetitive nerve stimulation at 3 Hz of the spinal accessory nerve revealed a 29% decrement at baseline, a 12% decrement after 10 sec of exercise, and a 48% decrement following 1 min. AchR-abs were absent, but MuSK-abs were detected.She was treated with plasmapheresis, solumedrol, and pyridostigmine and eventually discharged on prednisone 40 mg daily and cyclosporine 50 mg twice daily. She improved significantly over the next year but had occasional ptosis and mild residual proximal weakness. She was eventually tapered off prednisone.

A possible role of low regulatory T cells in anti-acetylcholine receptor antibody positive myasthenia gravis after bone marrow transplantation

“…A few reported patients with MG after transplantation revealed other antibodies toward non-AChR components of the postsynaptic muscle endplate, e.g. anti-MuSK and anti-striated muscle antibodies [15, 16]. These findings suggest that pathogenic autoantibodies toward the neuromuscular junctions may be produced when discontinuing or tapering immunosuppressive treatments after transplantation.…”

Immune-Mediated Complications after Hematopoietic Stem Cell Transplantation

“…Twenty-three cases of MG have been reported after allogeneic and autologous HSCT [77]. The majority of patients had positive acetylcholine receptor antibodies whereas 3 cases had musculoskeletal receptor antibodies [77][78][79]. The time from transplantation to diagnosis of MG ranged from several months to years.…”

Neuromuscular complications of hematopoietic stem cell transplantation

“…In patients younger than 40 years, HLA‐A1, HLA‐B8, and HLA‐DR3 are expressed more commonly . Nearly all of the reported patients had serum AchR‐Abs and only 3 reported patients had MuSK antibodies . Of the MuSK+ patients only 1 was reported to have evidence of cGVHD .…”

“…35 Nearly all of the reported patients had serum AchR-Abs and only 3 reported patients had MuSK antibodies. 33,37,38 Of the MuSK1 patients only 1 was reported to have evidence of cGVHD. 33 MG in these patients is typically responsive to pyridostigmine and prednisone.…”