The epidemiology and clinical features of selective immunoglobulin M deficiency: A single‐center study in China

BACKGROUND: Selective immunoglobulin M deficiency (SIgMD) is a rare primary immunodeficiency that is frequently reported in Western countries. However, large epidemiological and clinical studies of SIgMD in China are still lacking. Herein, we describe a cohort of SIgMD subjects in a large tertiary university hospital in China. METHODS: A cross‐sectional study included 139 668 participants at First Affiliated Hospital of Wenzhou Medical University from January 2014 to October 2018 was conducted. Individuals with a serum IgM level less than 0.3 g/L with normal levels of serum IgA and IgG were defined as having SIgMD. RESULT: A total of 63 subjects met the criteria for SIgMD(63/139668, 0.045%), with a male‐to‐female ratio of 0.85, aged from 19 to 99 years. The most common clinical manifestation was autoimmune disorders (38/63, 60.32%), while the second most common manifestation was infections (21/63, 33.33%). Neither allergies nor tumors were found among these 63 SIgMD subjects. Most importantly, there were 30 patients with systemic lupus erythematosus among these 63 SIgMD subjects, accounting for 47.62% of all SIgMD subjects. CONCLUSION: To our knowledge, we describe here the first large single‐center cohort of adult patients affected by SIgMD in China. The most common clinical manifestation was autoimmune disorders, specifically systemic lupus erythematosus.