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Table of Contents    
LETTER TO EDITOR
Year : 2014  |  Volume : 62  |  Issue : 2  |  Page : 218-219

Morvan syndrome plus thyroid dysfunction: A case with chronic mercury exposure


1 Department of Neurology, Chinese PLA General Hospital, Beijing, China
2 Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
3 Department of Neurology, The Affiliated Hospital of Weifang Medical University, Weifang, China

Date of Submission26-Nov-2013
Date of Decision21-Dec-2013
Date of Acceptance31-Mar-2014
Date of Web Publication14-May-2014

Correspondence Address:
Yifan Li
Department of Neurology, Chinese PLA General Hospital, Beijing
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.132439

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How to cite this article:
Li Y, Ren H, Ren M, Cui F, Yang F, Chen Z, Cui L, Huang X. Morvan syndrome plus thyroid dysfunction: A case with chronic mercury exposure. Neurol India 2014;62:218-9

How to cite this URL:
Li Y, Ren H, Ren M, Cui F, Yang F, Chen Z, Cui L, Huang X. Morvan syndrome plus thyroid dysfunction: A case with chronic mercury exposure. Neurol India [serial online] 2014 [cited 2021 Feb 28];62:218-9. Available from: https://www.neurologyindia.com/text.asp?2014/62/2/218/132439


Sir,

Morvan syndrome (MoS) usually correlates with the voltage-gated potassium channel (VGKCs) complex antibodies. [1] Mercury poisoning can present with such clinical syndrome.[2] Here, we present a woman who developed MoS and thyroid dysfunction after 2-months exposure to mercury.

A 33-year-old Chinese woman developed progressive hyperhidrosis and insomnia 3 days after insidious lower back pain and fatigue. Ten-days later she developed rapid muscle twitching and occasional cramps in the lower limbs followed by involvement of the arms, trunk, and face. Patient also experienced burning dysesthesia in all extremities. Two-months later she developed visual and auditory hallucinations at night with mood swings. Blood pressure fluctuated from normal to 170/100 mmHg, and heart rate from normal to 130 beats/minute. Mental status revealed elevated and irritable mood, with periods of disorientation to time, as well as mild cognitive deficits in short-term memory and attention. Extensive myokymia, decreased muscle tone, exercise-induced cramping in lower limbs, intention tremor, myoclonic jerks, impaired heel-knee-shin test, and diminished tendon reflexes were also noted. Serum thyroxin (171.2 nmol/l, reference 55.34-160.88) and free T4 (26.32 pmol/l, reference 10.42-24.32) were mildly elevated. Elevated supine angiotensin II was noted, 370.02 pg/ml (reference 15-97 pg/ml), whereas supine plasma renin activity and aldosterone levels were normal. Cerebrospinal fluid (CSF) analysis revealed elevated protein 642.5 mg/l (150-400 mg/l), raised IgG (4.52 mg/dl, reference 0.0-3.4), and IgA (0.57 mg/dl, reference 0.0-0.50), whereas the cell count was normal. Screening for autoantibodies showed positive serum contactin-associated protein 2 (CASPR2) antibodies detected by indirect immunofluorescence test (IIFT) and TITERPLANE technique (Euroimmun, Lübeck, Germany, FA 112d-1005-1) [Figure 1] and negative antinuclear antibodies (ANA), cytoplasmic antineutrophil cytoplasmic antibodies (c-ANCA), perinuclear ANCA (p-ANCA), thyroglobulin (Tg), thyroid peroxidise (TPO), and leucine-rich glioma inactivated 1 (LGI1) antibodies. Needle electromyography (EMG) showed spontaneous grouped discharges in the form of doublets, triplets, and multiplets throughout the body [Figure 2]. Electrocardiogram (ECG) revealed sinus tachycardia. A 24-h electroencephalogram (EEG) showed alpha/theta mixed EEG activity especially in frontal and central regions, without typical sleep elements.
Figure 1: The CASPR2 antibodies were detected in the serum of the patient diluted at 1:100

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Figure 2: Needle EMG showed grouped discharges on the left biceps femoris

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The diagnosis of MoS was confirmed. To thoroughly evaluate its possible cause, we completed numerous tests, including tumor markers, brain magnetic resonance imaging (MRI), chest and adrenal computed tomographies (CTs), abdominal and thyroid ultrasonographies, which were all negative. Screening for heavy metals showed elevated mercury levels in blood (3.9 ng/ml, reference <2.5) and urine (4.6 ng/ml, reference <2.5). The source of mercury was identified as the skin whitener purchased from internet (containing 1986 mg/kg mercury, 50 mg applied in total), which was unconsciously discontinued when the symptoms occurred. After treatment with intramuscular 2,3-dimercapto-1-propanesulfonic acid (DMPS) (500 mg/day, 3 days/week) for 2 weeks, the symptoms of hallucinations and insomnia disappeared, whereas the muscle twitching gradually stopped over the following 5 months. Thyroid function and needle EMG were normalized. Serum CASPR2 antibodies turned negative as well.

Review of the literature shows that mercuric salts can induce autoimmunity, [3] and environmental exposures to mercury correlates with serum levels of autoantibodies. [4] Here, we report an interesting case of MoS possibly associated with mercury exposure. We hypothesize that exposure to mercury, if it does not cause this autoimmune disease directly, may interact with other factors, either genetic or acquired, and induce or aggravate the nervous system damage. The efficacy of chelation treatment also supported this hypothesis. However, there is a possibility that the elevated mercury level was an unrelated phenomenon, as some cases of MoS remitted spontaneously. [5] Endocrine dysfunction was also noted in our patient, with elevation of the serum thyroxin and free T4 levels. The increased angiotensin II level might contribute to the high blood pressure of the patient. In conclusion, the mercury exposure may be a cofactor or precipitating factor in the pathogenesis of MoS. However, a population-based study should be carried out to find the association between prevalence of CASPR2 antibodies and mercury exposure.

 
 » References Top

1.Loukaides P, Schiza N, Pettingill P, Palazis L, Vounou E, Vincent A, et al. Morvan′s syndrome associated with antibodies to multiple components of the voltage-gated potassium channel complex. J Neurol Sci 2012;312:52-6.  Back to cited text no. 1
    
2.Garcin R, Boudene C, Ginsbourg M. Morvan′s fibrillary chorea and polyradiculoneuritis probably due to mercury poisoning. Rev Neurol (Paris) 1971;125:322-6.  Back to cited text no. 2
    
3.Havarinasab S, Hultman P. Organic mercury compounds and autoimmunity. Autoimmun Rev 2005;4:270-5.  Back to cited text no. 3
    
4.Silbergeld EK, Silva IA, Nyland JF. Mercury and autoimmunity: Implications for occupational and environmental health. Toxicol Appl Pharmacol 2005;207:282-92.  Back to cited text no. 4
    
5.Irani SR, Pettingill P, Kleopa KA, Schiza N, Waters P, Mazia C, et al. Morvan syndrome: Clinical and serological observations in 29 cases. Ann Neurol 2012;72:241-55.  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]

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