目的:探讨X连锁高IgM综合征（XHIGM）的临床特征、诊断要点、治疗方法等。方法:回顾性分析中国医学科学院血液病医院2020年3月收治的1例23岁XHIGM合并T细胞大颗粒淋巴细胞白血病（T-LGLL）患者的临床特征及实验室资料，并进行文献复习。结果:患者，男性，17岁开始出现反复感染症状，就诊后发现中性粒细胞减少、贫血伴有明显脾大，IgG、IgA水平减低。虽然IgM低于正常水平（典型XHIGM表现为IgM正常或升高），但通过二代测序证实该患者为CD40L基因纯合突变（染色体：chrX；位置：135730438；氨基酸变异情况：NM_000074：exon1：c.31C>T：p.R11X；突变类型：无义突变）；其母亲检测到该基因突变位点为杂合突变，其父亲未检测到该基因突变。患者明确诊断为XHIGM。患者脾切除术后贫血和中性粒细胞减少得以缓解，因白细胞升高，依据流式细胞术检测、TCR基因重排呈阳性和骨髓病理免疫组织化学染色结果表明T细胞大颗粒淋巴细胞增高且为克隆性增殖。患者最终诊断为XHIGM合并T-LGLL。结论:少数XHIGM患者可在成年后发病，且可表现为IgG、IgA和IgM水平均明显减低的非典型临床特征，CD40L基因突变是XHIGM最终的确诊标准。对于反复感染、IgG定量低于正常水平、合并中性粒细胞减少的男性患者，需进行XHIGM基因筛查。少数XHIGM患者可合并T-LGLL。“,”Objective:To investigate the clinical features, the key point of diagnosis and treatment methods of X-linked hyper-IgM syndrome (XHIGM).Methods:The clinical characteristics and laboratory data of a patient aged 23 years who was diagnosed as XHIGM complicated with T-cell large granular lymphocytic leukemia (TLGLL) in Institute of Hematology & Blood Diseases Hospital in March 2020 were analyzed retrospectively, and the literatures were reviewed.Results:This male patient presented with recurrent infection when he was 17 years old, and was found neutropenia, anemia accompanied by obvious splenomegaly, lower level of IgG and IgA after the visit. The level of IgM was lower than the normal level and the typical XHIGM was manifested with the normal or increased level of IgM, however CD40L homozygous mutation (chromosome: chrX; location: 135730438; variation of amino acid: NM_000074:exon1:c.31C>T:p.R11X; nonsense mutation) was confirmed by next generation sequencing. CD40L heterozygous mutation was detected in his mother, but it was not in his father. The patient was diagnosed as XHIGM. Anemia and neutropenia were alleviated after splenectomy in the patient, who was diagnosed as T-cell large granular lymphocyte elevation and clonal proliferation by flow cytometry, TCR gene rearrangement positive and bone marrow histopathological immunohistochemistry results because of the increasing leukocyte. The patient was eventually diagnosed as XHIGM complicated with T-LGLL.Conclusions:A small number of patients with XHIGM may develop symptoms in adulthood and may present with atypical clinical features of significant reduction in IgG, IgA, and IgM. The confirmed diagnosis of XHIGM is established by identification of CD40L gene mutation. XHIGM gene screening is required in male patients with recurrent infection, IgG level lower than normal and neutropenia. A few XHIGM patients are complicated with T-LGLL.