IgG4相关疾病（IgG4-related disease, IgG4-RD）是近年来逐渐被大家所认识的一种新的自身免疫病，可以累及全身多个系统，临床表现复杂多样，缺乏特异性。米库利兹病（Mikulicz disease, MD）被认为是IgG4-RD的一种亚型，有其独特的表现，包括唾液腺、泪腺、腮腺肿大，血清IgG4水平上升，腺体组织中大量IgG4+浆细胞浸润，糖皮质激素治疗有效［1］。然而，外分泌腺肿大还可见于多种因素，如病毒感染、淋巴瘤等，容易误诊、漏诊，延误治疗。现将北京大学人民医院收治的1例外院误诊为MD，我科确诊为非霍奇金淋巴瘤（non-Hodgkin’s lymphoma，NHL）的病例报告如下，并进行临床分析。

IgG4-related disease is a systemic disorder involving a spectrum of multiple indications, and various histopathological features are shared among different IgG4-related disease subtypes, which challenge diagnosis, although certain syndromes have organ-specific involvement. Among them, Mikulicz’s disease affecting the salivary and lacrimal glands, distinguished by often elevated levels of serum IgG4, infiltration of IgG4+ plasma cells into target tissues, and diffuse swelling, mass formation, or fibrosis of affected organs. However, there are several diseases, which could manifest as salivary gland swelling, mimicking Mikulicz’s disease, such as Sj-gren’s syndrome, mumps virus infection, obstruction of parotid duct, non-Hodgkin’s lymphoma (NHL), and so on. So differential diagnosis is important and essential as to the salivary gland swelling. In this paper, we analyzed a case of a 59-year-old male with symmetric salivary gland swelling. Mikulicz’s disease was misdiagnosed at the beginning without biopsy. Prednisone treatment ever seemed to be effective and antibiotics had no effect. Besides salivary involvement, the patient also manifested as testicle swelling and severe pancytopenia with the development of the disease, which rarely appeared in Mikulicz’s disease. Physical examination showed skin, sclera yellow dye, swollen submandibular, sublingual and lacrimal gland and splenomegaly. As a result, biopsy of right submandibular gland was made, and mucosa-associated lymphoid tissue lymphoma was confirmed by morphology and immunohistochemistry. Bone marrow biopsy also confirmed that lymphoma cells were found in the bone marrow. Finally, the diagnosis of mucosa-associated lymphoid tissue lymphoma (Phase ⅣE, Group A) was made on the patient, who was transferred to the hematology department for the treatment. NHL, especially, primary extranodal lymphoma usually involves the salivary gland, and painless swelling of the salivary gland is a common manifestation, similar with Mikulicz’s disease. So although salivary gland swelling is often associated with autoimmune diseases such as Sj-gren’s syndrome and IgG4-related disease, the awareness and suspicion of a possibility of NHL are essential for rheumatologists. Biopsy is a necessary examination to decrease or avoid misdiagnosis.