This is an observational case-control study, aiming to systematically analyze the gut microbiome characteristics of patients with monoclonal gammopathy of undetermined significance (MGUS). The study will collect blood and stool samples from MGUS patients, non-MGUS patients (with similar diseases), and healthy controls, and perform multi-omics detection including microbiomics, peptidomics, and biochemical immunology. It will comprehensively analyze the abnormal features of the gut microbiome in MGUS patients, which may help provide new biomarkers and potential mechanisms for the diagnosis, prognosis evaluation, and treatment strategies of MGUS.

This is a case-control, observational single-center study aiming to investigate the impact of common comorbidities on gut microbiome structure and disease progression in patients with monoclonal gammopathy. We plan to collect samples from 11 disease categories, with each category including two groups (monoclonal gammopathy and non-monoclonal gammopathy), as well as 700 age- and gender-matched healthy controls, for a total of 2,990 samples. At enrollment, we will collect whole blood, plasma, serum, and fecal samples from the study participants, and obtain relevant information such as demographic characteristics, lifestyle, family medical history, and medication use.We will perform metagenomic, proteomic, and serum biochemical and immunological analyses on the samples to directly obtain association data between gut microbiome characteristics (as exposure factors) and clinical outcomes (as endpoints). This study will systematically analyze the dysbiosis characteristics of the gut microbiome in monoclonal gammopathy patients, identify key microbial biomarkers, and compare the microbiome structure and clinical laboratory indices between MGUS patients and different comorbidity subgroups, to explore their impact on the disease diagnostic model.

(I) Inclusion Criteria:

1. Age 45 years or older;
2. Negative screening for monoclonal protein by MALDI-TOF MS;
3. No significant diseases found upon medical examination, and confirmed not to have any diseases related to this study;
4. Sufficient whole blood, plasma, serum, and stool samples available, and relevant case data can be provided.

(II) Exclusion Criteria:

1. History of intestinal tumors, irritable bowel syndrome, or inflammatory bowel disease, or diagnosed during hospitalization;
2. Antibiotic treatment received in the past month; Presence of severe systemic diseases, including malignant tumors;
3. Insufficient sample volume, or presence of severe hemolysis, lipemia, jaundice, or other unqualified sample conditions.

The study population will consist of patients aged 45 years and older who meet the following inclusion criteria:

1. Confirmed negative for monoclonal immunoglobulin by MALDI-TOF MS screening.
2. No significant diseases found upon medical examination, and confirmed not to have any diseases related to this study.
3. Availability of sufficient whole blood, plasma, serum, and fecal samples, as well as relevant case information.

Exclusion criteria include:

1. History of intestinal tumors, irritable bowel syndrome, or inflammatory bowel disease.
2. Received antibiotic treatment within the last month.
3. Presence of severe systemic diseases, including malignant tumors, insufficient sample volume, or presence of sample failure (e.g., severe hemolysis, lipemia, or jaundice).