Benign acute childhood myositis: laboratory and clinical features.
BACKGROUND
Benign acute myositis of childhood is a disorder of midchildhood, typically affecting boys. Symptoms include calf pain and difficulty walking after a viral illness. There is an epidemiologic association with influenza.


OBJECTIVE
To describe the clinical and laboratory features of benign acute myositis.


RESULTS
Thirty-eight children (32 boys, 6 girls) were seen with 41 episodes of myositis between 1978 and 1997. Two were siblings and three had recurrent episodes. Mean age at onset of symptoms was 8.1 years. Children remained ambulant during 33 of 41 episodes. Two characteristic gaits were noted: toe-walking in 13, with a wide-based stiff-legged gait in another 7. Muscle tenderness was isolated to the gastrocnemius-soleus muscles in 82% of episodes. Recovery occurred within 1 week. Creatine kinase levels were elevated during all episodes. Viral studies were positive in 10 of 24 episodes, 5 because of influenza B.


CONCLUSIONS
Benign acute myositis is a syndrome of midchildhood that can be differentiated from more serious causes of walking difficulty by the presence of calf tenderness, normal power, intact tendon reflexes, and elevated creatine kinase. The gait patterns noted may minimize power generation of the calf muscles by splinting the ankles. Onset in childhood may reflect an age-related response to viral infection, and occurrence primarily in boys may reflect a genetic predisposition or an as-yet unknown metabolic defect.
Mackay
M T
MT
Department of Neurology, Royal Children's Hospital, Parkville, Victoria, Australia.
Kornberg
A J
AJ
Shield
L K
LK
Dennett
X
X
D000208:Acute Disease; D001706:Biopsy; D002648:Child; D003402:Creatine Kinase / Q000097:blood; D005260:Female; D020275:Guillain-Barre Syndrome / Q000175:diagnosis / Q000209:etiology / Q000473:pathology; D006801:Humans; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis / Q000473:pathology; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D009220:Myositis / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology
D003402:Creatine Kinase