在没有感染病因的情况下，病例中出现了全身性肥大细胞增生症模拟反应性关节炎的情况。回顾患者的病历记录。我们报告了一个全身性肥大细胞增生症复发的病例，患者出现了伴随着膝盖单关节炎、膀胱炎和双侧结膜炎的全血细胞减少症状，这些症状同时在2-4天的时间间隔内发生，模拟出了反应性关节炎的表现，而没有感染病因。我们的病例展示了反应性关节炎的特征（尿道炎、结膜炎和关节炎三联症），但并没有感染的触发因素，而是肥大细胞增生症的复发。在没有感染病因的情况下，我们在面对这样的临床情况时应该放宽思路。在排除潜在感染后，应考虑有恶性肿瘤的反应性关节炎。版权所有 © 2023 Oussama G. Nasrallah et al.

Illustration of a case of systemic mastocytosis mimicking reactive arthritis in the absence of an infectious etiology.Review of the patient's medical records.We report a case of systemic mastocytosis relapse, presenting with pancytopenia accompanied by knee monoarthritis, cystitis, and bilateral conjunctivitis occurring simultaneously at the same time interval within 2-4 days, mimicking reactive arthritis in the absence of an infectious etiology.Our case demonstrated reactive arthritis features (triad of urethritis, conjunctivitis, and arthritis) without an infectious trigger but rather a relapse of mastocytosis. We should think outside the box when faced with such a clinical scenario in the absence of an infectious etiology. Paraneoplastic reactive arthritis is to be considered after excluding an underlying infection.Copyright © 2023 Oussama G. Nasrallah et al.