Medical Journal of Dr. D.Y. Patil Vidyapeeth

CASE REPORT
Year
: 2020  |  Volume : 13  |  Issue : 6  |  Page : 697--699

A case of generalized myasthenia gravis with bilateral optic neuritis – A rare association


Atanu Chandra1, Anirban Ghosh2, Uddalak Chakraborty3, Indranil Sen4,  
1 Department of General Medicine, R.G.Kar Medical College and Hospital, Shyambazar, Kolkata, West Bengal, India
2 Department of General Medicine, ESI-PGIMSR and ESIC Medical College and Hospital, Joka, Kolkata, West Bengal, India
3 Department of General Medicine, Post Graduate Trainee, R.G. Kar Medical College and Hospital, Shyambazar, Kolkata, West Bengal, India
4 Department of General Medicine, North Bengal Medical College and Hospital, Siliguri, West Bengal, India

Correspondence Address:
Atanu Chandra
Senbagan, Udayachal, S.M Bose Road, (Near 5 No. Railway Gate), Agarpara, Kolkata-700109, West Bengal
India

Abstract

Myasthenia gravis (MG) is a relatively uncommon autoimmune disorder of neuromuscular junction characterized by fatigable muscle weakness, bulbar symptoms, and weakness of extraocular muscles with a significant diurnal variation. Among all other autoimmune disorders associated with optic neuritis, the association of MG with optic neuritis is very rare, with only a few cases have been reported till date. We present a rare case of 37 years old female who was admitted in November 2018 with generalized MG (seronegative) along with isolated bilateral optic neuritis, and the patient responded significantly to steroids, immunomodulators, and anticholinergics.



How to cite this article:
Chandra A, Ghosh A, Chakraborty U, Sen I. A case of generalized myasthenia gravis with bilateral optic neuritis – A rare association.Med J DY Patil Vidyapeeth 2020;13:697-699


How to cite this URL:
Chandra A, Ghosh A, Chakraborty U, Sen I. A case of generalized myasthenia gravis with bilateral optic neuritis – A rare association. Med J DY Patil Vidyapeeth [serial online] 2020 [cited 2021 Jan 16 ];13:697-699
Available from: https://www.mjdrdypv.org/text.asp?2020/13/6/697/300141


Full Text



 Introduction



Myasthenia gravis (MG) is a relatively uncommon autoimmune disease that is mediated mainly by autoantibodies against acetylcholine receptors on the postsynaptic membrane of the neuromuscular junction, with features of fatigable muscle weakness and ptosis.[1],[2] We hereby present an interesting case of generalized MG associated with bilateral optic neuritis in 37 years old female.

 Case Report



A 37-year-old female, homemaker presented with a history of weakness, drooping of both eyelids along with the difficulty of chewing and swallowing, intermittent diplopia, and nasal regurgitation for the past 3–4 months. There was also a complaint of the dimness of vision for the past 15 days before admission. The weakness was fatigable in nature, along with significant diurnal variation. There was also a significant improvement in weakness after taking rest. On physical examination, she had a significant motor weakness (mainly proximal) of all four limbs along with bulbar weakness and ophthalmoplegia without any subjective or objective evidence of sensory or sphincter involvement. Forward arm abduction test, ice pack test, and edrophonium test were positive. Fundoscopy did not reveal any significant abnormality. Confrontation and instrumental visual perimetry could not be performed at the time of presentation due to the severe diminution of vision. In the first instance, the complaint of the dimness of vision was thought to be due to intermittent diplopia, secondary to ophthalmoparesis. Routine hematological and biochemical results were normal. The thyroid profile did not show any abnormality. Serum ANA (antinuclear antibody), rheumatoid factor, and antithyroid antibodies were negative. The repetitive nerve stimulation test came out to be positive. The patient was provisionally diagnosed as a case of generalized MG and started on pyridostigmine in the doses of 240 mg/day (in four divided doses). In the meantime, anti-acetylcholine receptor antibody and anti-muscle-specific kinase (MuSK) antibody came out to be negative. Computerized tomography (CT) of the thorax did not reveal any thymic enlargement or hilar lymphadenopathy.

The patient had significant improvement of all symptoms on follow up after 1 week except the symptom of the dimness of vision. There was a decrease in visual acuity in both eyes to 6/18 (best-corrected visual acuity). Color vision was grossly impaired. Magnetic resonance imaging (MRI) of the brain revealed mild thickening and hyperintensity of optic nerve sheath in the retrobulbar region on both sides with mild post-contrast enhancement of optic nerves-consistent with bilateral optic neuritis and no brain parenchymal lesion [Figure 1]. MRI of the cervical spine did not reveal any abnormality. visual evoked potential (VEP) study of both eyes revealed bilateral anterior pathway dysfunctions [Figure 2]. Serum anti neuromyelitis optica (NMO) (Aquaporin 4) immunoglobulin G (IgG) and serum myelin oligodendrocyte glycoprotein IgG were negative. Cerebrospinal fluid had a normal opening pressure, and analysis did not reveal any evidence of infective or inflammatory process. HIV1 and 2 serology were negative. As there was no obvious clinical or laboratory evidence of immunosuppressive or overt infective process, the patient was started with high dose intravenous methylprednisolone (1 gm/day) for 5 days followed by oral prednisolone 50 mg/day. The presence of other autoimmune diseases such as Sjogren's syndrome, systemic lupus erythematosus, antineutrophil cytoplasmic antibody related vasculitis, etc., were excluded by serological tests. Anti-auaporin4 antibody and CSF study for the oligoclonal band were negative.{Figure 1}{Figure 2}

The symptoms of the dimness of vision improved significantly. The patient was prescribed oral prednisolone of 50 g/day (1 mg/kg body weight) for 2 months followed by slow tapering of steroids along with azathioprine 100 mg/day (started on week 4) along with pyridostigmine in the above-mentioned doses.

 Discussion



The clinical features of our patients are in keeping with the diagnosis of MG coexisting with bilateral optic neuritis. To the best of our knowledge, this is the first such reported case from our region.

MG is an autoimmune disease of the neuromuscular junction in which circulating antibodies cause fluctuating skeletal muscle weakness. Most of the patients with MG develop ophthalmologic manifestations of the disease, a disorder of neuromuscular transmission characterized by the fatigable weakness of skeletal muscles.[1] Variability in muscle weakness is a hallmark of myasthenia. The pathophysiology of adult MG is the destruction of AChR at the postsynaptic muscle membrane due to circulating anti-AChR antibodies[2] or, less commonly, antibodies to anti- MuSK, or LRP4 (low-density lipoprotein receptor-related protein 4).[3]

Bilateral optic neuritis is relatively uncommon in adults.[4] In our patient, there was no evidence of any toxic, infectious, or neoplastic disorder. Sarcoidosis seemed unlikely in view of the negative chest CT and the normal serum angiotensin-converting enzyme levels. NMO also seemed improbable in this circumstance considering the normal spinal cord MRI, negative NMO antibodies, and the absence of recurrent episodes during the follow-up period. Moreover, NMO spectrum disorders are usually associated with posterior visual pathway dysfunction and area postrema syndrome with comparatively poor response to glucocorticoids, which were not very much evident in our case.[5] The mean age of onset of optic neuritis is in the third decade of life but can occur from the first to the seventh decades. The annual incidence of optic neuritis ranges from 1.4 to 6.4 new cases per 100,000 population.[6]

Since date, there are only a few case reports describing the coexistence of MG with NMO. The age of onset of NMO is most common around the fourth decade of life with a female predominance.[7] Ogaki et al.[8] reported a case of NMO developing in MG who had thymectomy, but Kay et al.,[9] reported another case of NMO without a thymectomy having been done. The association between NMO and MG is unclear since antibodies produced in these conditions target different and specific substrates. The exact mechanism for the coexistence of the two conditions is not fully known but maybe due to possible shared autoimmune predisposition.[8],[10]

In our case, the patient was anti-acetylcholine receptor-negative, and bilateral optic neuritis was not also due to the NMO spectrum of diseases. We speculate that dysregulation of B cell autoimmunity is the main factor in MG, and possibly some other autoantibodies or some unknown autoimmune mechanism predisposed our patient to optic neuritis that is also autoimmune in etiology. This is further evidenced by a significant improvement in both muscle weakness and visual acuity with the commencement of high dose methylprednisolone for 5 days followed by maintenance oral prednisolone and immunosuppressive therapy. Although it is a rare presentation clinically, there can be an association of concurrent autoimmune disorders with optic neuritis.[11]

In our case, the patient was thoroughly evaluated for other autoimmune disorders, but all markers were negative. This report describes a patient with MG, which manifested as features of intermittent diplopia, weakness followed by the dimness of vision. In patients with MG, the involvement of optic nerves is very rare. Clinicians should, therefore, be aware of this potential manifestation. In addition, patients of MG with persistent dimness of vision despite treatment with acetylcholinesterase inhibitors should prompt investigation for concomitant visual pathway defects.

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.

References

1Meriggioli MN, Sanders DB. Autoimmune myasthenia gravis: Emerging clinical and biological heterogeneity. Lancet Neurol 2009;8:475-90.
2Vincent A. Autoimmune disorders of the neuromuscular junction. Neurol India 2008;56:305-13.
3Pevzner A, Schoser B, Peters K, Cosma NC, Karakatsani A, Schalke B, et al. Anti-LRP4 autoantibodies in AChR-and MuSK-antibody-negative myasthenia gravis. J Neurol 2012;259:427-35.
4de la Cruz J, Kupersmith MJ. Clinical profile of simultaneous bilateral optic neuritis in adults. Br J Ophthalmol 2006;90:551-4.
5Wingerchuk DM, Banwell B, Bennett JL, Cabre P, Carroll W, Chitnis T, et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders. Neurology 2015;85:177-89.
6Brewis M, Poskanzer DC, Rolland C, Miller H. Neurological disease in an English city. Acta Neurol Scand 1966;42:Suppl 24:1-89.
7Leite MI, Coutinho E, Lana-Peixoto M, Apostolos S, Waters P, Sato D, et al. Myasthenia gravis and neuromyelitis optica spectrum disorder: A multicenter study of 16 patients. Neurology 2012;78:1601-7.
8Ogaki K, Hirayama T, Chijiiwa K, Fukae J, Furuya T, Noda K, et al. Anti-aquaporin-4 antibody-positive definite neuromyelitis optica in a patient with thymectomy for myasthenia gravis. Neurologist 2012;18:76-9.
9Kay CS, Scola RH, Lorenzoni PJ, Jarius S, Arruda WO, Werneck LC. NMO-IgG positive neuromyelitis optica in a patient with myasthenia gravis but no thymectomy. J Neurol Sci 2008;275:148-50.
10Mapelli G, De Palma P, Franco F, Fini M. Myasthenia gravis and recurrent retrobulbar optic neuritis: An unusual combination of diseases. Ophthalmologica 1986;192:234-7.
11Zahid S, Iqbal M. Systemic lupus erythematosus presenting as optic neuropathy: A case report. Cureus 2019;11:e4806.