Rheumatoid arthritis is the most common type of inflammatory arthritis affecting about 1% of the population. With the advent of disease-modifying anti-rheumatic drugs the disease can be well controlled in many cases. Patients, however, are prone to developing infectious complications. In rare cases, these can mimic a flare of the underlying itself. We report the case of a 45-year-old female patient with a history of seronegative rheumatoid arthritis (RA) who presented with swelling and tenderness of the third metacarpophalangeal joint of the right hand. A flare of her RA was suspected based on clinical and ultrasound findings which showed a tenosynovitis with intense power doppler activity. Her steroid dose was increased but the clinical response to glucocorticoid therapy was very limited. Subsequently, she developed skin manifestations of ‘swimmer’s granuloma’ over the next 2 weeks after first presentation. Finally, a diagnosis of a Mycobacterium marinum infection was established with the help of tissue biopsy and culture, and the patient received appropriate antibiotic treatment with the desired effect. This case highlights the difficulty of distinction between infection and inflammation in patients with joint swelling and pain, especially in the age of disease-modifying drugs (DMARDs) and the concomitant risk of atypical infections. A review of the literature identified eight additional published cases, which suggests that Mycobacterium marinum infection is a rare but recognized complication of DMARD therapy. It can mimic a flare of the underlying arthritis potentially leading to diagnostic delays, and requires differential diagnostic methods to identify the pathogen and pave the way for appropriate treatment.

中文翻译：

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耀斑还是敌人？- 模仿类风湿性关节炎腱鞘炎的海分枝杆菌感染：病例报告和文献复习

类风湿性关节炎是最常见的炎症性关节炎类型，影响约 1% 的人口。随着改善疾病的抗风湿药物的出现，这种疾病在许多情况下可以得到很好的控制。然而，患者容易出现感染性并发症。在极少数情况下，这些可以模仿底层本身的耀斑。我们报告了一名 45 岁女性患者，她有血清反应阴性类风湿性关节炎 (RA) 病史，表现为右手第三掌指关节肿胀和压痛。根据临床和超声检查结果怀疑她的 RA 发作，结果显示腱鞘炎伴有强烈的能量多普勒活动。她的类固醇剂量增加了，但对糖皮质激素治疗的临床反应非常有限。随后，在首次就诊后的 2 周内，她出现了“游泳者肉芽肿”的皮肤表现。最后，在组织活检和培养的帮助下，确定了海分枝杆菌感染的诊断，并且患者接受了适当的抗生素治疗，达到了预期的效果。该病例突出了关节肿胀和疼痛患者的感染和炎症之间的区分困难，特别是在疾病缓解药物 (DMARDs) 的时代以及伴随的非典型感染风险。对文献的回顾发现了另外 8 个已发表的病例，这表明海分枝杆菌感染是 DMARD 治疗的一种罕见但公认的并发症。它可以模仿潜在的关节炎发作，可能导致诊断延误，