|Year : 1985 | Volume
| Issue : 2 | Page : 109-11
Congenital myasthenia gravis (a case report).
RM Joshi, BA Bharucha, MD Mohire, NB Kumta
R M Joshi
|How to cite this article:|
Joshi R M, Bharucha B A, Mohire M D, Kumta N B. Congenital myasthenia gravis (a case report). J Postgrad Med 1985;31:109-11
|How to cite this URL:|
Joshi R M, Bharucha B A, Mohire M D, Kumta N B. Congenital myasthenia gravis (a case report). J Postgrad Med [serial online] 1985 [cited 2022 Dec 4 ];31:109-11
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Myasthenia gravis is characterised by abnormal fatiguability after repeated or sustained muscle activity and improvement after rest. Peak incidence is seen in young adults but it may also occur in infancy and childhood. One can recognize three separate entities in childhood period: (a) transient neonatal myasthenia in an infant of myasthenic mother, (b) congenital or infantile myasthenia in an infant of non-myasthenic mother and (c) juvenile myasthenia similar to adult myasthenia. Rarity of this condition and a good therapeutic response to neostigmine prompted us to report the following case.
A 15 month old male child was brought to us by his mother with a history of drooping of both eyelids, noticed since the age of 6 months, appearing late in the day but disappearing after sleep. The child was a full-term normal delivery born of a non-consanguinous marriage, and the primi-mother had noticed quickening at 26 weeks of gestation. There was no history suggestive of myasthenia in the mother. Neonatal period was uneventful and the milestones were normal upto 6 months of age but after that the child had achieved only walking with support by 15 months of age, while other developments were normal. There was no history of swallowing difficulty, aspiration or respiration difficulty except on admission when the child had signs of right upper zone pneumonitis.
On CNS examination, the child had the findings of bilateral ptosis, weak gag reflex, generalised hypotonia with weakness also of intercostal muscles and diaphragm, with depressed deep tendon reflexes.
With a clinical diagnosis of congenital myasthenia gravis in an infant of a non-myasthenic mother, the child was investigated. Neostigmine test with 0.375 mg given intramuscularly showed a good response in the form of improvement in ptosis, gag reflex, power, respiration and deep tendon reflexes.
X-ray chest showed right upper zone pneumonitis which cleared up with antibiotics.
Repeatative stimulation of the median nerve with recording of muscle action potentials from abductor pollicis brevis showed a definite decrement at 3 cps frequency. This decrement was subsequently abolished by intramuscular injection of prostigmine.
The child was put on neostigmine tablets, 5 mg 4 times a day during waking hours and he showed a good response in the form of improvements in signs.
Congenital myasthenia presenting in an infant of non-myasthenic mother is rare (1% of cases). Simpson has postulated an auto-immune etiology of adult myasthenia gravis; but there is no association with thymoma or antibodies in congenital myasthenia, as seen in adult cases., Bundy undertook a detailed genetic study based on available reports in the literature and some cases from 4 London hospitals and suggested an autosomal recessive pattern of inheritance. Macrae recorded a case with weakness at birth in which foetal movements were markedly diminished in the last 6 weeks of pregnancy.
In an isolated case, the diagnosis may be difficult. It should be kept in mind in an infant with unexplained sucking, swallowing or respiratory difficulty, especially if with ptosis, ophthalmoplegia or hypotonia. It should be differentiated from transient neonatal myasthenia as seen in [Table 1] The diagnosis is confirmed by a response to anticholinesterase drugs. Edrophonium chloride, 0.2 mg per kg intravenously or neostigmine 0.04 mg per kg intramuscularly may be used. EMG is a helpful adjunct to the diagnosis. There is a progressive decrease in muscle response on repetitive stimulation of the nerve at low rates.
The therapy consists of oral pyridostigmine, 1 mg per kg every four hours or neostigmine, 0.3 mg/kg every 3 hours during waking hours in the day and injections before feeds if required. Streoids, immunosuppressants, plasmapheresis or thymectomy are not as helpful in these cases.,,,, Drugs such as curare, gallamine, succinyl choline, quinine, quinidine, neomycine, procaine and morphine should be avoided.
The course tends to be non-fluctuating and compatible with a long survival with little need for medication compared to other forms. However, a number of recent reports on fatal cases due to acute bulborespiratory involvement suggests that prognosis is not always good.
We thank the Dean, Seth G.S. Medical College and K.E.M. Hospital, Bombay, for giving us permission to publish this paper.
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