共济失调-毛细血管扩张症（A-T）是一种罕见的常染色体隐性DNA修复障碍，其特征为逐渐进行性小脑退行性变、毛细血管扩张、免疫功能缺陷、反复发作的鼻窦肺感染、对辐射敏感、早衰和易患癌症。虽然偶尔有报道与自身免疫和慢性炎症性疾病（如白癜风、血小板减少症和关节炎）相关联，但关节受累在初次发病时的情况很少见。我们在此报告了一个7岁的白种女孩的病例，她因有发热的咳嗽和多关节炎病史而被收入风湿科。她有明显的多关节炎，包括膝关节畸形，并伴有严重肺炎。胸部计算机断层扫描显示双侧支气管扩张、实质性实变和间质性肺病；类风湿因子和I型干扰素签名结果为阴性，因此排除了COatomer蛋白亚单位α（COPA）综合征的可能性。根据组织学证据显示结节性肝炎病变，怀疑为结节病，但检测到的血清血管紧张素转化酶和几聚酶的正常水平剔除了这种可能性。根据她过去4年内至少6次肺炎的病史，进行了免疫表型分析。结果显示完全缺乏IgA和IgE，且对于肺炎球菌、破伤风毒素和B型流感嗜血杆菌疫苗的特异性抗体功能缺陷。此外，还发现B细胞和最近来的胸腺迁出细胞（RTE）数量较少（CD4Ra 1.4%），同时CD4+/CD8+T细胞比率较低（< 1）。最后，基于步态障碍（摇摆的宽基步行），检测了血清α-胎蛋白水平，结果增加至276 ng/ml（正常值< 7 ng/ml）。诊断为共济失调-毛细血管扩张症，加之有球部毛细血管扩张症的存在，并通过全外显子测序（WES）得到了证实。虽然罕见，但即使在无球部或皮肤毛细血管扩张症的情况下，对于存在肺支气管扩张和步态障碍的情况，应始终考虑A-T。自身免疫和肉芽肿性疾病必须作为鉴别诊断考虑。©2023。 Società Italiana di Pediatria.

Ataxia-telangiectasia (A-T) is a rare autosomal recessive DNA repair disorder, characterized by progressive cerebellar degeneration, telangiectasia, immunodeficiency, recurrent sinopulmonary infections, radiation sensitivity, premature aging and predisposition to cancer. Although the association with autoimmune and chronic inflammatory conditions such as vitiligo, thrombocytopenia and arthritis has occasionally been reported, an onset with articular involvement at presentation is rare.We herein report the case of a 7-year-old Caucasian girl who was admitted to the Rheumatology Department with a history of febrile chough and polyarthritis which led initially to the suspicion of an autoinflammatory disease. She had overt polyarthritis with knees deformities and presented with severe pneumonia. A chest Computed Tomography (CT) scan showed bilateral bronchiectasis, parenchymal consolidation and interstitial lung disease; rheumatoid factor and type I interferon signature resulted negative, therefore excluding COatomer Protein subunit Alpha (COPA) syndrome. A diagnosis of sarcoidosis had been suspected based on histological evidence of granulomatous liver inflammation, but ruled out after detecting normal angiotensin converting enzyme and chitotriosidase blood levels. Based on her past medical history characterized by at least six episodes of pneumonia in the previous 4 years, immunological phenotyping was performed. This showed complete IgA and IgE deficiency with defective antigen-specific antibodies to Pneumococcal, Tetanus toxin and Hemophilus Influenzae B vaccines. Additionally, low numbers of B cells and recent thymic emigrants (RTE) were found (CD4Ra 1.4%), along with a low CD4+/CD8 + T cells ratio (< 1). Finally, based on gait disturbances (wobbly wide-based walking), serum alfa-fetoprotein was dosed, which resulted increased at 276 ng/ml (normal value < 7 ng/ml). A diagnosis of Ataxia-Telangiectasia was made, strengthened by the presence of bulbar telangiectasia, and then confirmed by Whole Exome Sequencing (WES).Although rare, A-T should always be ruled out in case of pulmonary bronchiectasis and gait disturbances even in the absence of bulbar or skin telangiectasia. Autoimmune and granulomatous disorders must to be considered as differential diagnosis.© 2023. Società Italiana di Pediatria.