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| CASE REPORT |
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| Year : 2017 | Volume
: 14
| Issue : 4 | Page : 232-233 |
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Bulbar myasthenia after 7 years of thymectomy
Ramesh Babu Mutiki, A Panneer
Department of Neurology, Apollo Main Hospital, Chennai, Tamil Nadu, India
| Date of Web Publication | 5-Feb-2018 |
Correspondence Address:
A Panneer
Institute of Neurosciences, Apollo Hospitals, Chennai - 600 006, Tamil Nadu
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/am.am_6_17
A small proportion of thymoma patients without myasthenia gravis (MG) have been observed to develop MG after total removal of the thymoma. However, the underlying cause is not yet known due to the rarity of postoperative MG patients. We report a 49-year-old female in who developed MG, 7 years after surgical removal of thymoma. Computed tomography and magnetic resonance imaging showed no features of recurrent or metastatic thymoma. Administration of pyridostigmine bromide resulted in prompt improvement of myasthenic symptoms. Our observations indicate that postoperative follow-up care with monitoring of possible postoperative MG is necessary after thymectomy. Keywords: Myasthenia gravis, thymectomy, thymoma
How to cite this article:
Mutiki RB, Panneer A. Bulbar myasthenia after 7 years of thymectomy. Apollo Med 2017;14:232-3 |
| Introduction | |  |
Myasthenia gravis (MG) is an autoimmune disease in which muscular weakness and fatiguability of skeletal muscles are caused by antibodies against acetylcholine receptor (AChR) at the neuromuscular junction. A thymoma, which is an epithelial tumor of the thymus gland, is usually benign, occurs in about 15% of adult patients with MG.[1] It has long been suspected that the thymus or a thymoma may play a role in the pathogenesis of MG. Although thymectomy may improve the myasthenic symptoms, MG can develop from months to years after the removal of a thymoma in previously nonmyasthenic patients.[2],[3],[4],[5] A nonresidual tumor or thymic tissues have been found in some patients, while MG heralded recurrent or metastatic thymoma in other cases.[6],[7] We defined cases of MG onset after total removal of thymoma as “postoperative MG.” We report a patient whom developed myasthenia after total removal of the thymus gland for thymoma without tumor recurrence.
| Case Report | | |
A 49-year-old female presented with complaints of change in voice for 1 month – her voice felt “horrible and nasty,” and she was not able to speak loudly and had difficulty being understood by others. The main vocal aspects indicated by the patient were vocal fatigue, hoarseness, voice failure, vocal tremor, and the need to make an effort to speak. She also complained of cough while eating with nasal regurgitation. All these symptoms were more by the end of the day and felt better by morning. No H/S/O Neck or respiratory muscle weakness. No H/O difficulty or heaviness in opening her eyes, diplopia. No fatiguability or weakness of limbs. She had thymectomy done 7 years before the onset of present symptoms, which was identified on routine health checkup. Histopathology of resected gland showed features suggestive of a low-grade thymoma. She was on treatment hypothyroidism for the past 4 years. Physical examination revealed a body mass index of 28.6 kg/m2, voice fatigability, Nasal Twang speech, and Single breath count of 56/breath. Central nervous system and other systemic examination were normal. Results from repetitive nerve stimulation and neostigmine tests were consistent with neuromuscular junction disorder. The titer of anti-AChR antibody was high, at 43.7 nmol/L. The diagnosis of MG was confirmed by the findings of both the anti-AChR antibody and electrophysiological test. Chest computed tomography and magnetic resonance imaging showed no signs of recurrent or metastatic thymoma. Pyridostigmine bromide administration (180 mg/day) was started, which resulted in the prompt improvement of myasthenic symptoms.
| Discussion | | |
The thymus plays a key role in the immunologic status of an individual, and disease of the thymus can be associated with autoimmune disorders. MG first appearing many years following the removal of a thymoma reportedly occurs in 1.5%–28% of cases.[8] The interval between a thymectomy and the onset of postoperative MG has varied between studies. Two of the studies having adequate sample size and detailed clinical data found that the mean interval between thymectomy and the onset of postoperative MG was 19 and 18 months. Namba et al. reported that patients with a shorter onset of postoperative MG had a better prognosis, but other studies did not find this relationship.[3],[8] The rarity of postoperative MG cases has meant that it remains unclear whether the interval between thymectomy and the onset of postoperative MG influences the prognosis. We speculate that this discrepancy is due to different therapies being applied for MG. Most reports demonstrate that postoperative MG responds to anticholinesterase drugs and/or steroids and that the prognosis is relatively good.[5],[8] Although a thymectomy does not prevent the onset of postoperative MG, this procedure is associated with a good prognosis. One study found that 63%, 25%, and 12% of thymomas were of mixed histological type, predominantly lymphocytic type, and predominantly epithelial type, respectively,[3] and the corresponding percentages in another study were 65%, 22%, and 13%.[8] These distributions of the histological types were similar to that in patients with thymoma and preoperative MG. In the study of Kondo and Monden, the anti-AChR antibody levels at onset varied between 1.8 and 91 nmol/L.[8] The majority of patients show a clinical severity of type I or type IIA on Osserman's classification. However, they found that the titer of anti-AChR antibody did not correlate with clinical severity, as was the case in our patient. The mechanism underlying the onset of postoperative MG is unclear. The various time periods between a thymectomy and the onset of postoperative MG raise doubts as to whether a thymectomy directly triggers MG onset. Two useful studies were recently published. Hoffacker et al. found using T-cell-proliferation assays for a fragment of the AChR that the thymoma released mature auto-antigen-specific T-cells into the periphery.[9] Buckley et al. found that T-cells in a thymoma were exported to the peripheral blood and that these T-cells could persist in the periphery for many years.[10] These studies suggest that a thymoma actively exports large numbers of mature T-cells into the peripheral blood, with these cells persisting in the periphery, potentially stimulating autoantibody production and subsequent autoimmune disease. The late onset of MG and other autoimmune disorders should be kept in mind as possible complications of surgical treatment for thymoma.
| Conclusion | | |
Therefore, careful follow-up with consideration of occurrence of MG is necessary after resecting a thymoma. In postoperative MG cases, recurrent or metastatic thymoma should be ruled out because reoperation can be effective even in the treatment of MG.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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