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|LETTER TO EDITOR
|Year : 2016 | Volume
| Issue : 4 | Page : 783-785
Myasthenia gravis accompanied by Graves' disease, thyrotoxic hypokalemic periodic paralysis and thymic hyperplasia
Kun Huang, Yue-Bei Luo, Huan Yang, Xiao-Su Yang, Jing Li
Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
|Date of Web Publication||5-Jul-2016|
Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Huang K, Luo YB, Yang H, Yang XS, Li J. Myasthenia gravis accompanied by Graves' disease, thyrotoxic hypokalemic periodic paralysis and thymic hyperplasia. Neurol India 2016;64:783-5
|How to cite this URL:|
Huang K, Luo YB, Yang H, Yang XS, Li J. Myasthenia gravis accompanied by Graves' disease, thyrotoxic hypokalemic periodic paralysis and thymic hyperplasia. Neurol India [serial online] 2016 [cited 2020 May 28];64:783-5. Available from: http://www.neurologyindia.com/text.asp?2016/64/4/783/185401
A 33-year-old married Mongolian male patient suffered from a nonfluctuating ptosis of the left upper eyelid for 28 years and a paroxysmal weakness of the limbs, especially in the lower extremities for 10 days. The patient was diagnosed as a case of myasthenia gravis (MG) when he was 5 years old and was on intermittent pyridostigmine bromide treatment. He did not have limb muscle weakness until 10 days before coming to our ward. The muscle weakness resolved the next day, after a good night's sleep, without any treatment. He also started experiencing hyperhydrosis and irascibility in the recent 3 months. There was no remarkable family history. Physical examination showed ptosis of the left upper eyelid that covered the upper one-third of the pupil, bilateral ophthalmoptosis and exophthalmos, and a mild dysarthria. Muscle power testing was normal. The new quantitative MG (QMG) score of the Myasthenia Gravis Foundation of America was 8.
Electromyography (EMG) demonstrated myopathic changes in the proximal limbs and a positive repetitive nerve stimulation test [Figure 1]. The mediastinal computed tomography (CT) suggested thymic hyperplasia (TH) [Figure 2]. The neostigmine test was positive and acetylcholine receptor (AChR) antibody (AChR-Ab) testing was negative (0.08 nmol/L). Anti-muscle specific kinase antibody test was not performed because the assay was unavailable. Color Doppler ultrasonography showed a diffusely enlarged goiter and cervical lymph nodes. Thyroid function tests revealed elevated free thyroxine (T) 3, free T4, thyroid peroxidase antibodies as well as thyroid stimulating hormone (TSH) receptor antibodies, and the depression of TSH.
|Figure 1: Electromyography found muscle lesions in the proximal limbs, and a declining response following repetitive nerve stimulation. (a) right ulnar nerve above, (b) left accessory nerve above|
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The patient was diagnosed as having MG, Graves' disease (GD), and TH. Treatment was initiated including pyridostigmine bromide, prednisone, potassium supplementation methimazole, and propranolol. Partial clinical remission was achieved.
However, bilateral lower limb weakness reappeared 5 days after the initiation of the treatment, without any obvious precipitating factors. The neurological examination revealed that the muscle strength of the upper limbs, proximal lower limbs, and distal lower limbs was 4/5, 0/5, 3/5, respectively. Increased muscle tone was noted and tendon reflexes were normal. Given the possibility of a myasthenic crisis or periodic paralysis, neostigmine was injected intramuscularly. A second physical examination 40 min after neostigmine injection showed no muscle strength improvement. An emergent electromyogram revealed a conspicuous U wave [Figure 3]. Serum ion test from blood drawn during the onset of the disease revealed a decreased serum potassium level (2.11 mmol/L). Potassium solution was given orally and via an intravenous infusion. The muscle weakness completely resolved by the next morning and serum potassium returned back to the normal range. The patient had a similar attack of muscle weakness 5 days later. The muscle strength was normalized again after potassium solution treatment. Corticosteroids were tapered and the ptosis and weakness almost disappeared; the QMG score was 3. All blood parameters were normal except for the depression of TSH. The patient received thymectomy several days later. Pathological examination showed TH [Figure 4]. The patient was placed on a monthly followed up. Three months later, the prednisone was stopped and he remained symptom-free.
|Figure 3: Electrocardiography taken when the episodes of limps weakness occurred showed the U-wave|
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MG patients are often associated with TH and other autoimmune disorders such as GD and thyrotoxic hypokalemic periodic paralysis (THPP). However, the coexistence of all of the three diseases has rarely been reported.,, It was reported that 65% of MG patients have TH and 10%, a thymoma., AChR-Abs are found in the serum of approximately 85% of MG patients; a small proportion of MG patients who are seronegative for AChR-Ab have circulating antibodies to MuSK or lipoprotein receptor-related protein (LRP4)., In this case, the patient had a TH which is the most common type of thymic disease associated with MG. The present patient had THPP attacks more frequently after the treatment with prednisone. Considering that corticosteroids could lower serum potassium level, we considered that the frequent THPP attacks were due to the combined effects of MG, GD, and prednisone.
In conclusion, for a patient with a history of MG with recurrent or acute flaccid muscle paralysis, it is important to consider hypokalemic periodic paralysis as one of the possible causes. In other words, clinicians should bear in mind other diagnostic possibilities also when observing a patient with MG with a fluctuating muscle weakness.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]