IgG4-Related Disease in a 90-Year-Old Man with an 18-Year Disease Course: A Case Report.

IgG4-related disease (IgG4-RD) is a multi-organ inflammatory immune-mediated illness caused by IgG4-secreting plasma cells infiltrating the tissue. This condition usually affects elderly men. A 90-year-old Chinese male was diagnosed with IgG4-RD based on the new 2019 ACR/EULAR classification criteria, as he had multiple organ involvement. After receiving treatment with glucocorticoids, leflunomide, and gamma-globulin, the patient's clinical symptoms significantly improved, confirming the accuracy of the diagnosis. The patient had an 18-year medical history during which the disease progressively worsened due to delayed diagnosis and treatment. Although the relevant symptoms were alleviated with appropriate medication, the overall treatment process encountered challenges. Due to the patient's relative lack of adrenocortical function, he experienced symptoms such as nausea, exhaustion, and loss of appetite during the hormone reduction process. Therefore, timely intervention is especially crucial to address the side effects of hormone therapy.