Background Benign acute childhood myositis (BACM) is a transient condition mainly affecting children of school age characterized by muscle pain, typically localized to the calf muscle with symmetrical lower extremity pain and difficulty in walking. Usually, the symptomatology is preceded by a viral infection including influenza, parainfluenza, rotavirus, and mycoplasma.

Methods The case series was conducted in four pediatric hospitals in Catania, Italy, over a 12-year observational period. Clinical examination, laboratory data, course, treatment, and complications of the affected children were extracted from electronic medical records of each hospital.

Results For the case series, 50 children diagnosed with BACM were enrolled: the mean age of affected children was 5.35 years, 86% of were males, and in 56% the affections occurred during the winter. In the affected children, the clinical picture was characterized by previous fever and/or symptoms of inflammation of the upper airways, and followed by pain in the lower extremities up to uncoordinated gait. In 17 cases the etiological agent was isolated, including the influenza virus type B as the most frequent and influenza virus type A, Mycoplasma pneumoniae, beta-hemolytic streptococcus, and herpes simplex virus. Children were treated with supportive therapy. In all the children the muscular symptomatology had a good evolution with progressive marked reduction of pain and of the high level of CKemia. Neither clinical recurrences nor sequelae were reported.

Conclusion BACM shows to have in most of the cases a favorable evolution, a spontaneous remission of symptoms, and a good prognosis. However, the disorder generates parental distress for the acute presentation and the striking muscle dysfunction. It is worthy a rapid and early diagnosis to avoid unnecessary diagnostic investigations and a careful follow-up necessary to exclude persistence of symptoms or creatine kinase elevation.

背景 良性急性儿童肌炎 (BACM) 是一种主要影响学龄儿童的暂时性疾病，其特征是肌肉疼痛，通常局限于小腿肌肉，伴有对称性下肢疼痛和行走困难。通常，症状学先于病毒感染，包括流感、副流感、轮状病毒和支原体。

方法 该病例系列是在意大利卡塔尼亚的四家儿科医院进行的，为期 12 年的观察期。从各医院的电子病历中提取受影响儿童的临床检查、实验室数据、病程、治疗和并发症。

结果 病例系列纳入了 50 名诊断为 BACM 的儿童：受影响儿童的平均年龄为 5.35 岁，其中 86% 为男性，56% 的感染发生在冬季。在受影响的儿童中，临床表现的特征是之前有发烧和/或上呼吸道炎症症状，随后出现下肢疼痛直至步态不协调。17例分离出病原体，其中B型流感病毒最常见，A型流感病毒肺炎支原体 、β-溶血性链球菌和单纯疱疹病毒。儿童接受了支持疗法。在所有儿童中，肌肉症状学都有良好的发展，疼痛明显减轻，CKemia 水平升高。既没有临床复发也没有后遗症的报道。

结论 BACM 在大多数病例中表现出良好的演变、症状的自发缓解和良好的预后。然而，这种疾病的急性表现和显着的肌肉功能障碍会使父母感到痛苦。值得进行快速和早期诊断以避免不必要的诊断调查，并进行必要的仔细随访以排除症状持续存在或肌酸激酶升高。