CASE REPORT

Niger J Paed 2013; 40 (2): 201 –203

Oluwayemi IO

Ade-Ojo IP

Ajayi IA

Myasthenia gravis following chicken

pox infection in a Nigerian primary

school girl

DOI:http://dx.doi.org/10.4314/njp.v40i2,21

Accepted: 12th November 2012

Abstract We report a case of my-

asthenia gravis occurring post

drooping of both upper eye lids

which worsens as the day pro-

gresses and has persisted for more

than one year. There was good

response to Neostigmine.

(

Oluwayemi IO

Ade-Ojo IP, Ajayi IA

)

Chicken pox infection in a 9 year

old Nigerian girl. The girl was

growing and seeing normally until 2

weeks after a chicken pox infection

when she observed progressive

Departments of Paediatrics,

Obstetrics, Gynaecology,

Ophthalmology, Ekiti State University

Teaching Hospital, Ado-Ekiti

Introduction

bilaterally. Other systems were essentially normal.

Myasthenia gravis (MG) is an autoimmune neuromuscu-

lar disorder resulting in fluctuating muscle weakness

and fatigability. The weakness is caused by circulating

A diagnosis of myasthenia gravis probably secondary to

thymoma was made.

antibodies that block acetylcholine receptors at the post-

synaptic neuromuscular junction inhibiting the excita-

tory effects of the neurotransmitter acetylcholin₂ e on

nicotinic receptors in neuromuscular junctions. The

incidence of myasthenia gravis is 3-30 cases per million

Investigations: Antibodies against Acetylcholine recep-

tor was not detected; Full blood count showed relative

lymphocytosis (PCV 44%, total WBC 5,300; Neutrophil

24%. Lymphocytes 72%, Monocytes 4%); Erythrocyte

sedimentation rate 11mm/hr; Electrolyte and urea within

normal limit; Chest X-ray, no abnormality detected,

Magnetic resonance imaging of the skull and Computed

tomography of the chest revealed a normal study.

She was given intravenous Neostigmine 0.05mg/kg

(2.5mg) slowly with remarkable improvement: the two

upper eyelids opened widely within 5 minutes of ad-

ministration of Neostigmine. Thereafter she was placed

on oral Neostigmine 7.5mg qds with sustained clinical

improvement and patient continued to do well, able to

see without lifting her chin upward. She was also re-

viewed by an ophthalmologist .

per year. Myasthenia gravis occurs in both genders and

affects all races. All age groups can be affected but most

commonly people from 50 to 70 years. In females inci-

dence of MG peaks in the third decade o₄f life, whereas it

peaks in the 6 and 7 decades in males.

Case Presentation

A.M., a nine year old primary 6 girl presented with 13

month history of variable drooping of both upper eye

lids and double vision. She observed difficulty in lift-

ing up both upper eye lids after engaging in some ac-

tivities as the day progresses making it difficult for her

to see clearly. She therefore had to lift her chin upward

to allow her to see. She usually felt normal, able to see

without difficulty, on waking up from sleep but be-

comes weak and easily gets tired as the day progresses

particularly when she engages in her daily activities.

There was associated double vision and difficulty seeing

distant objects. She had chicken pox two weeks be-

fore onset of above symptoms. In addition she also

complained of painful swallowing and chest pain.

Before administration of

Neostigmine.

Examination revealed a young girl who was not small

for age, not pale, afebrile, anicteric . Significant find-

ings were on ocular examination . With manual eleva-

tion of the eyelids visual acuity were normal with

glasses. She had bilateral ptosis, ophthalmoplegia,

pupils were 3mm equal bilaterally and reacting normally

to light. Posterior ocular segments were normal

After administration of

Neostigmine

Discussion

ciated with MG includes: female, and people with cer-

tain human leucocyte antigen types (HLA-BB, HLA-

DRw3, and HLA-DQw2). We could not do an HLA

typing in this patient. MG is also associated with various

autoimmune diseases like Hashimoto’s thyroiditis,

Grave’s disease, rheumatoid arthritis, diabetes₁_,₄mellitus

type I, Lupus and demyelinating CNS diseases.

Myasthenia gravis is idiopathic in most patients. In

children, three types of myasthenic syndrome can be

distinguished: 1. Neonatal: Pregnant mothers with my-

asthenia gravis in 12% of cases pass the antibodies to

the infant through the placenta, causing neonatal myas-

thenia gravis. The symptoms will start in the first two

days and disappear within a few weeks. 2. Congenital:

this occurs very rarely in children of healthy mothers

with symptoms beginning at birth. It is not caused by an

autoimmune process but due to synaptic malformation,

which in turn is caused by genetic mutations and the

inheritance pattern is typically autosomal recessive. 3.

Juvenile myasthenia gravis: it occurs in children but

after the peripartum pe₁riod. The hallmark of myasthenia

gravis is fatiguability. In our patient eyelid muscle

weakness was the first symptom noticed. This has been

reported to be the case in most cases, while in a few

others difficulty in swallowing and slurred speech may

be the first presentation. The muscles become progres-

sively weaker during periods of activity and improved

after periods of rest. The muscles controlling movement

of the eyeballs and eye lids, facial expressions, chewing,

Diagnosis of myasthenia gravis can be difficult as the

symptoms can be subtle. A thorough physical examina-

tion can reveal easy fatigability, with the weakness im-

provin_,₄g after rest and worsening again on repeat exer-

cise. There was improvement in the symptoms of the

above patient after rest. Our patient possibly fell in the

group of patients with negative antibodies to acetylcho-

line receptors much more so that her symptoms were

predominantly ocular. In suspected cases serology can

be performed to detect antibodies against the acetylcho-

line receptor. This test has a sensitivity of 80-95% in

generalized severe cases but may be negative in up to

50% of ocular myasthenia gravis. Patients who are

negative for anti-acetylcholine receptor antibodies may

be seropositive for antibodies against MuSK protein.

Electromyography considered to be the most sensitive

talking, and swallowing are particularly susceptible.

Often, physical examination yields normal finding. The

degree of muscle involvement varies raging from local-

ized form limited to the eye muscles (ocular myasthenia)

to a generalized, severe form affecting many muscles,

sometimes including respiratory muscles.

test is not very specific for MG. Endrophonium test is

limited to situation where oth_,₇er investigations do not

yield a conclusive diagnosis. In this test intravenous

endrophonium chloride or Neostigmine is administered;

these drugs block the breakdown of acetylcholine by

cholinesterase and temporarily increase the levels of

acetylcholine at the neuromuscular junction thereby re-

lieving weakness temporarily in ocular myasthenia gra-

The patient reported above did not have respiratory mus-

cle involvement but obviously seemed to have some

weakness of other muscles because of the history of

easy fatiguability after engaging in her daily activities.

Symptoms varies including; asymmetrical ptosis, diplo-

pia (due to weakness of muscle that control movement

of the eyeballs), unstable/ waddling gait, weakness in

arms, hands, fingers, legs, and neck, a change in facial

expression, dysphagia, shortness of breath and dy-

sarthria. The patient above did not have any thymus

involvement even though it has been reported that up

to 75% of myasthenia gravis patients have an_,₄abnormal-

vis. A chest X-ray may identify widening of mediasti-

num suggestive of thymoma, but CT or MRI are more

sensitive ways to ide_,n₈tify thymomas which are closely

associated with MG. MRI of the cranium and orbits is

also performed to exclude compressive lesions of the

cranial nerves and ocular muscles. All these tests were

negative in the case reported.

Treatment involves use of cholinest_,e₄rase inhibitors such

as Neostigmine or Pyridostigmine. Corticosteroids are

typically used in moderate or severe cases of MG that

fail to respond adequately to acetylcholine inhibitors and

ity of the thymus and 10% have a thymoma. In myas-

thenic crisis there is paralysis of the respiratory muscles

necessitating assisted ventilation to sustain life. Crisis is

often triggered by infection, fever, adverse drug reaction

or emotional stress in patients whose respiratory mus-

cles are already weak. Cardiac muscle is generally not

affected by MG since it is regulated by autonomic nerv-

thymectomy. Thymectomy is the standard treatment for

all patients with thymoma and for patients aged 10-

,4,

55years without thymoma but generalized MG. Im-

munoglobulin is useful during myasthenia crisis in pa-

tients with severe weakness poorly controlled with other

agents. The effect is rapid₁_,₄b_,₆ut transient and the same is

The reported case re-

ous system. Myasthenia gravis is an autoimmune chan-

true for plasmapharesis.

nelopathy featuring antibodies directed against the

body’s own proteins. Our patient had a history of

chicken pox two weeks before onset of myasthenic

symptoms. The causative role of this preceding infec-

tion cannot be proven. Although it has been proposed

that sensitization to a foreign antigen which has cross

reactivity with acetylcholine receptor could be a cause

of MG but there is yet no known infective agent that

sponded very well to Neostigmine tablets with relieve of

symptoms.

Conclusion

we report this case of MG following chicken pox infec-

tion in a nine year old Nigerian girl to serve as a tem-

plate for further investigation into the yet unknown

pathogen associated with MG.

could account for this. Various drugs may also induce

or exacerbate symptoms of MG₄ which often resolve

after discontinuation of the drugs. Other findings asso-