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Table of Contents    
LETTER TO EDITOR
Year : 2017  |  Volume : 65  |  Issue : 5  |  Page : 1152-1153

Stiff-person syndrome after thymectomy in myasthenia gravis mimicking a post-thymectomy myasthenic crisis


1 Department of Neurology, Chungbuk National University Hospital, Cheongju, Republic of Korea
2 Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine; Neuroscience Center, Samsung Medical Center, Seoul, Republic of Korea
3 Department of Neurology, Changwon Gyeongsang Institute of Health Science, Gyeongsang National University School of Medicine, Changwon, Republic of Korea
4 Department of Neurology, Chungbuk National University Hospital, Chungbuk National University College of Medicine, Cheongju, Republic of Korea
5 Department of Neurology, The Catholic University of Korea, College of Medicine, Bucheon St. Mary's Hospital, Bucheon, Republic of Korea

Date of Web Publication6-Sep-2017

Correspondence Address:
Ju-Hong Min
Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
Republic of Korea
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/neuroindia.NI_493_16

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How to cite this article:
Lee HL, Min JH, Seok JM, Cho EB, Lee Ss, Cho HJ, Kim BJ. Stiff-person syndrome after thymectomy in myasthenia gravis mimicking a post-thymectomy myasthenic crisis. Neurol India 2017;65:1152-3

How to cite this URL:
Lee HL, Min JH, Seok JM, Cho EB, Lee Ss, Cho HJ, Kim BJ. Stiff-person syndrome after thymectomy in myasthenia gravis mimicking a post-thymectomy myasthenic crisis. Neurol India [serial online] 2017 [cited 2019 Sep 18];65:1152-3. Available from: http://www.neurologyindia.com/text.asp?2017/65/5/1152/214053


Sir,

Stiff-person syndrome (SPS) is a rare neurological disorder, which is characterized by continuous systemic muscle stiffness and painful paroxysmal spasm with co-contraction of agonist and antagonist muscles.[1] Most patients with SPS have antibodies directed against the enzyme glutamic acid decarboxylase (GAD), which can be used to confirm the diagnosis of SPS.[2],[3]

We present a case of SPS after thymectomy in a patient with myasthenia gravis (MG). To our knowledge, this is the first report of SPS after thymectomy associated with MG.

A 48-year old woman attended the emergency room because of generalized weakness with dyspnea. Two months previously, she had been diagnosed with MG. The thymoma was revealed on computer tomography, and thymectomy was performed 1 month prior to the current admission. The histology of the thymoma was of cortical type, World Health Organization (WHO) grade B1 (Masaoka grade I). Her neurological examination during the visit showed bilateral ptosis, dyspnea, and generalized weakness with intermittent muscle stiffness. Arterial blood gas analysis showed respiratory acidosis. A diagnosis of MG crisis after thymectomy was made and intravenous immunoglobulin G (IVIG) therapy was started together with ventilator care. However, the patient complained of frequent painful muscle spasms. One month after IVIG therapy, all her symptoms improved.

Four months after IVIG therapy, she was readmitted with dyspnea with muscle stiffness and painful spasms. She showed co-contraction of agonist and antagonist muscles in the abdomen and thorax. The motor examination showed proximal weakness caused by MG. Anti-acetylcholine receptor antibody (Anti-AchR) antibody was elevated to 10.184 nmol/L and anti-GAD (glutamic acid decarboxylase) antibody was 300 U/mL (reference range: <1.0 U/mL). Magnetic resonance imaging of the head and spinal cord revealed no abnormality and electroencephalography and nerve conduction studies were normal. Finally, she was diagnosed with SPS. She was treated with IVIG therapy, which relieved the clinical symptoms.

SPS is a rare neurologic syndrome that is frequently found in association with autoimmune disorders or tumors.[2] However, post-thymectomy MG crises are not uncommon; the incidence varies from 3.1 to 30.3%.[4] This patient was initially diagnosed with a post-thymectomy MG crisis because her dyspnea requiring mechanical ventilation developed within one month after thymectomy. However, she also complained of muscle stiffness and cramps, and was therefore, finally diagnosed with SPS after thymectomy in MG.

Only 4 cases of coexisting SPS and MG with thymoma have been reported previously [Table 1].[5],[6],[7],[8] In these cases, SPS developed before the symptoms of MG and the thymoma was discovered in the process of evaluating the cause of the SPS; moreover, the symptoms of SPS improved in all these patients after thymectomy. It is interesting that our patient was diagnosed with MG with thymoma, and subsequently, SPS developed after thymectomy. Unlike the previous cases, the serology showed that our patient was positive for both anti-GAD and anti-AchR antibodies.
Table 1: Review of literature on stiff-person syndrome and myasthenia gravis with thymoma

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The pathogenesis of SPS is not fully understood. Neuropharmacological studies have shown evidence of an imbalance between catecholamine excitatory and gamma-aminobutyric acid inhibitory neurotransmitter systems in the brainstem and spinal cord.[3]

There have been several reports of post-thymectomy MG where patients developed myasthenic symptoms after thymectomy. It was suggested that large numbers of mature autoantigen-specific T cells enter the peripheral blood and that these cells can persist in the periphery for many years, even though thymectomy has been performed.[9] Therefore, considering that, in our patient, SPS developed after thymectomy, it is possible that other paraneoplastic antibodies such as the anti-GAD antibody associated with thymoma may persist for several years after thymectomy.

In addition, there have been recent reports that a systemic autoimmune disease developed after thymectomy in patients with MG or other immunological diseases,[10] suggesting that there was a marked acceleration of the disease possibly caused by the elimination of the thymic T-suppressor cell population.[10] Therefore, the development of SPS after thymectomy could be associated with an autoimmune mechanism.

There is no established standard therapy for SPS. Various agents including benzodiazepines, antispasmodic agents, intramuscular botulinum toxin A, antiepileptic drugs, and immunosuppressive agents have been used. We treated our patient with IVIG and steroid pulse therapy for the aggravation of SPS, and with multiple drugs for symptomatic management.

This is the first report of a patient with MG and thymoma, who developed SPS after thymectomy and had both anti-GAD and anti-AchR antibodies. These paraneoplastic syndromes may both be the result of an autoimmune mechanism that is associated with thymoma. Initially, the patient's symptoms mimicked those of a postoperative MG crisis; however, her muscle stiffness was eventually determined to be caused by SPS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Iwata T, Inoue K, Mizuguchi S, Morita R, Tsukioka T, Suehiro S. Thymectomy for paraneoplastic stiff-person syndrome associated with invasive thymoma. J Thorac Cardiovasc Surg 2006;132:196-7.  Back to cited text no. 1
    
2.
Baizabal-Carvallo JF, Jankovic J. Stiff-person syndrome: Insights into a complex autoimmune disorder. J Neurol Neurosurg Psychiatry 2015;86:840-8.  Back to cited text no. 2
    
3.
Aso Y, Sato A, Narimatsu M, Takiguchi Y, Yamaguchi Y, Inukai T, et al. Stiff-man syndrome associated with antecedent myasthenia gravis and organ-specific autoimmunopathy. Intern Med 1997;36:308-11.  Back to cited text no. 3
    
4.
Nam TS, Lee SH, Kim BC, Choi KH, Kim JT, Kim MK, et al. Clinical characteristics and predictive factors of myasthenic crisis after thymectomy. J Clin Neurosci 2011;18:1185-8.  Back to cited text no. 4
    
5.
Nicholas AP, Chatterjee A, Arnold MM, Claussen GC, Zorn GL, Oh SJ. Stiff-persons' syndrome associated with thymoma and subsequent myasthenia gravis. Muscle Nerve 1997;20:493-8.  Back to cited text no. 5
    
6.
Tanaka H, Matsumura A, Okumura M, Kitaguchi M, Yamamoto S, Iuchi K. Stiff man syndrome with thymoma. Ann Thorac Surg 2005;80:739-41.  Back to cited text no. 6
    
7.
Piccola G, Cosi V. Stiff-Man syndrome, dysimmune disorder, and cancer. Ann Neurol 1989;26:105.  Back to cited text no. 7
    
8.
Thomas S, Critchley P, Lawden M, Farooq S, Thomas A, Proudlock FA, et al. Stiff person syndrome with eye movement abnormality, myasthenia gravis, and thymoma. J Neurol Neurosurg Psychiatry 2005;76:141-2.  Back to cited text no. 8
    
9.
Yamada Y, Yoshida S, Iwata T, Suzuki H, Tagawa T, Mizobuchi T, et al. Risk factors for developing postthymectomy myasthenia gravis in thymoma patients. Ann Thorac Surg 2015;99:1013-9.  Back to cited text no. 9
    
10.
Park M-J, Kim Y-A, Lee S-S, Kim B-C, Kim M-K, Cho K-H. Appearance of systemic lupus erythematosus in patients with myasthenia gravis following thymectomy: Two case reports. J Korean Med Sci 2004;19:134-6.  Back to cited text no. 10
    



 
 
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