Pattiyakumbura T T, Jayasundara J M L C K, Premarathne P B U S, Abeywardana S, Jayamaha C J S
Department of Virology, Medical Research Institute, Colombo 08, Colombo, 00800, Sri Lanka.
Teaching Hospital, Rathnapura, 70000, Sri Lanka.
J Med Case Rep. 2025 Aug 5;19(1):394. doi: 10.1186/s13256-025-05072-x.
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.
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.
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.
肌炎以骨骼肌炎症和无力为特征，是由各种感染性、自身免疫性和神经肌肉疾病引起的多因素病症。其中，感染性肌炎是一种罕见但重要的临床实体，主要由病毒病原体引起。流感病毒、肠道病毒、风疹病毒和人类免疫缺陷病毒等病毒是常见病因，流感相关性肌炎是一种有充分文献记载的现象。尽管在许多情况下它具有自限性，但由于其潜在并发症和所带来的诊断挑战，流感相关性肌炎仍值得临床关注。与甲型流感相比，乙型流感是一种抗原性变异较小的亚型，越来越被认为是急性肌炎的病因，尤其是在儿童人群中。
我们报告一例来自斯里兰卡中部的9岁斯里兰卡女孩，她有4天的发热、咳嗽和感冒病史，随后出现双侧小腿疼痛和行走困难。检查时，她双侧小腿压痛，肌张力、肌力和反射正常，无感觉障碍。基本血液学检查结果正常，但她的肌酸激酶水平显著升高，达8370 U/L，表明有明显的肌肉损伤。超声成像显示小腿肌肉炎症。鼻咽拭子检测乙型流感病毒RNA呈阳性，证实了病毒病因。支持性治疗使患者在出院后10天内症状完全缓解。
流感相关性肌炎是流感季节出现肌肉疼痛和步态障碍儿童的重要鉴别诊断。对该病的早期识别和实验室确诊可避免不必要的检查，并有助于及时进行患者管理。本病例突出了乙型流感相关性肌炎的临床和诊断方面，强调了在患有急性肌炎的儿科患者中考虑病毒病因的重要性。
