Immunoadsorption With a Tryptophan‐Immobilized Column Using Conventional and Selective Plasma Separators in the Treatment of Myasthenia Gravis

Dear Editor, Autoimmune neurological diseases are often treated by immunoadsorption (IA) using a conventional plasma separator and tryptophan-immobilized column (1). Recently, in vitro studies revealed that immunoadsorption by tryptophan-immobilized column using a selective plasma separator (SeIA) could eliminate IgG to a degree similar to that in IA while retaining fibrinogen (2,3). However, no previous reports have evaluated treatment with SeIA in clinical practice. Here we present a case of myasthenia gravis (MG) using IA and SeIA in the treatment. The patient was a 74-year-old male with MG diagnosed by clinical symptoms, physiological findings, and a positive reaction to antibodies against acetylcholine receptors (AChRAb). The patient developed an infection and was treated with antibiotics, which induced an acute exacerbation of MG resulting in hospital admission. The severity of MG did not improve with the administration of 10 mg oral prednisolone on alternating days following intravenous immunoglobulin (Ig) therapy, and the quantitative MG score changed from 13 to 15. The disease was finally controlled after a combination of 3 mg/day oral tacrolimus, 25 mg/day oral prednisolone, and six sessions of immunoadsorption using tryptophan-immobilized column (IA–SeIA–SeIA– SeIA–SeIA–IA) on alternating days. The score improved from 15 to 8, and the patient was discharged. IA was performed by Immusorba TR-350 column (IM-TR; Asahi Kasei Medical, Tokyo, Japan) using OP-05 W (Asahi Kasei Medical) as a conventional plasma separator, and SeIA was performed by IMTR using Evacure plus EC-4A10 (EC-4A; Kawasumi Laboratories) as a selective plasma separator (2,3). The sieving coefficients of IgG, factor XIII (FXIII), and fibrinogen using EC-4A were 0.5, 0.17, and 0, respectively (4). IM-TR has a high affinity to AChRAb and fibrinogen (1,2). We evaluated the reductions of AChRAb, IgG, fibrinogen, and FXIII after IA and SeIA. Figure 1 shows the percent reductions of these factors after one session of the following therapies: IA when the mean processed plasma volume (PPV) was approximately 1.9 L and SeIA when the PPV was 2 L. The removal rates for AChRAb were similar at approximately 45–47% after one session of IA and SeIA, whereas the removal rates for fibrinogen and FXIII in SeIA were lower than those in IA. This is the first report to investigate the reductions of AChRAb, IgG, FXIII, and fibrinogen by SeIA in clinical practice. SeIA could remove AChRAb to a degree similar to that by IA while retaining coagulation factors such as fibrinogen and FXIII. Furthermore, this is also the first report on the use of the combination of IA and SeIA in a patient with MG. Repeated IA can easily and significantly reduce fibrinogen, whereas SeIA can retain both fibrinogen and FXIII. SeIA can be a useful and safe modality of immunoadsorption when disease-specific autoantibodies are limited to IgG and IM-TR has a high affinity to these antibodies. Further studies are necessary to investigate the removal dynamics, therapeutic effects and complications of SeIA.