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Influenza B-associated acute myositis in a child in Sri Lanka: a case report
T T Pattiyakumbura1, J M L C K Jayasundara2, P B U S Premarathne2
1Department of Virology, Medical Research Institute, Colombo 08, Colombo, 00800, Sri Lanka. thulanipattiyakumbura@yahoo.com.
Background:
Myositis, characterized by inflammation and weakness of skeletal muscles, is a multifactorial condition caused by various infectious, autoimmune, and neuromuscular disorders. Among these, infective myositis is a rare but significant clinical entity, predominantly caused by viral pathogens. Viruses such as influenza, enteroviruses, rubella, and human immunodeficiency virus are common culprits, with influenza-associated myositis being a particularly well-documented phenomenon. Despite its self-limiting nature in many cases, influenza-associated myositis warrants clinical attention owing to its potential complications and the diagnostic challenges it presents. Influenza B, a less antigenically variable subtype compared with influenza A, has been increasingly recognized as a cause of acute myositis, especially in pediatric populations.
Case Presentation:
We report the case of a 9-year-old Sri Lankan girl from central Sri Lanka who presented with a 4-day history of fever, cough, and cold, followed by bilateral calf pain and difficulty walking. On examination, she exhibited bilateral calf tenderness with normal muscle tone, power, and reflexes, without sensory impairment. Basic hematological investigations were within normal limits, but her creatine kinase levels were markedly elevated at 8370 U/L, indicating significant muscle damage. Ultrasound imaging revealed inflammation of the calf muscles. A nasopharyngeal swab tested positive for influenza B RNA, confirming the viral etiology. Supportive care resulted in complete symptom resolution within 10 days of hospital discharge.
Conclusion:
Influenza-associated myositis is an important differential diagnosis for children presenting with muscle pain and gait disturbances during the influenza season. Early recognition and laboratory confirmation of the condition can prevent unnecessary investigations and facilitate prompt patient management. This case highlights the clinical and diagnostic aspects of influenza B-associated myositis, underscoring the importance of considering viral etiologies in pediatric patients with acute myositis.
Insights
Influenza B can cause acute myositis in children, leading to muscle pain and difficulty walking. Prompt diagnosis through viral testing is key for effective management of this influenza-associated condition.
Area of Science:
- Pediatric Infectious Diseases
- Neuromuscular Disorders
- Viral Pathogenesis
Background:
- Myositis involves skeletal muscle inflammation and weakness from diverse causes.
- Infective myositis, though rare, is often viral, with influenza being a common culprit.
- Influenza B is increasingly identified as a cause of acute myositis in children.
Purpose of the Study:
- To highlight influenza B-associated myositis as a critical differential diagnosis in pediatric patients.
- To emphasize the importance of early recognition and laboratory confirmation for managing acute myositis.
- To present a case illustrating the clinical and diagnostic features of influenza B-associated myositis.
Main Methods:
- Case report of a 9-year-old girl with fever, cough, and calf pain.
- Clinical examination revealed calf tenderness with normal neurological findings.
- Laboratory tests showed elevated creatine kinase (8370 U/L) and positive influenza B RNA in nasopharyngeal swab.
Main Results:
- The patient presented with symptoms consistent with acute myositis.
- Elevated creatine kinase levels and ultrasound confirmed significant muscle inflammation.
- Influenza B viral RNA confirmed the etiology, leading to supportive care and full recovery.
Conclusions:
- Influenza-associated myositis should be considered in children with muscle pain during flu season.
- Early laboratory confirmation prevents unnecessary investigations and guides treatment.
- This case underscores the need to consider viral causes in pediatric acute myositis.
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