Muscle specific kinase autoimmune myasthenia gravis in children: A case series

Abstract We report clinical, neurophysiological and autoantibody profiles of 9 children presenting with fatigable weakness and MuSK autoantibody seropositivity. Eight were female, 3 were black; median onset age was 8 years. Diplopia or bulbar dysfunction were common presenting symptoms. Half of the...

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Bibliographic Details
Published in:Neuromuscular disorders : NMD 2013-11, Vol.23 (11), p.874-882
Main Authors: Skjei, Karen L, Lennon, Vanda A, Kuntz, Nancy L
Format: Article
Language:English
Subjects:
Adolescent
Autoantibodies - blood
Autoimmune Diseases - immunology
Autoimmune myasthenia gravis
Child
Child, Preschool
Children
Electromyography
Female
Humans
Infant
Male
Muscle-specific kinase autoantibodies
Myasthenia Gravis - diagnosis
Myasthenia Gravis - immunology
Neurology
Receptor Protein-Tyrosine Kinases - immunology
Receptors, Cholinergic - immunology
Young Adult
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Summary:Abstract We report clinical, neurophysiological and autoantibody profiles of 9 children presenting with fatigable weakness and MuSK autoantibody seropositivity. Eight were female, 3 were black; median onset age was 8 years. Diplopia or bulbar dysfunction were common presenting symptoms. Half of the patients experienced moderate to severe weakness of bulbar, facial and respiratory muscles (including exacerbations requiring mechanical ventilation). Muscle AChR antibodies were detected transiently in 2 patients but no other autoantibodies were detected. Clinical response to treatment was variable and incomplete. No thymic abnormalities were noted by CT or pathologically (3 underwent thymectomy). Electromyographic (EMG) abnormalities (decrement of compound muscle action potential amplitude during slow repetitive nerve stimulation and variation in individual motor unit potentials) were limited to clinically weak muscles. Single fiber EMG demonstrated abnormalities in an asymptomatic muscle in the single patient studied. As in adults, MuSK autoimmune MG presents more commonly in females, and weakness preferentially affects bulbar, facial and respiratory muscles. Morbidity is significant and responses to standard therapies are variable and incomplete. Neurophysiological confirmation is more challenging in children because testing of weak muscles (cranial nerve-innervated and respiratory) may require moderate sedation and monitoring.
ISSN:0960-8966
1873-2364
DOI:10.1016/j.nmd.2013.07.010