The Rheumatic Manifestations in Patients with Combined Immunodeficiency.

Combined immunodeficiencies (CIDs) represent a rare group of inherited immune disorders in which defects in T- and B-lymphocyte function lead to recurrent infections, immune dysregulation, and an increased tendency toward autoimmune and rheumatologic complications. A retrospective cross-sectional analysis was performed on 150 patients with CID, diagnosed according to the European Society for Immunodeficiencies (ESID) criteria and followed at the Children's Medical Center and Mofid Children's Hospital (Tehran, Iran) between 2009 and 2020. Clinical records, immunologic evaluations, and rheumatologic findings were reviewed, with particular attention to autoantibody detection and disease frequency. Among 150 patients, 42 (28%) exhibited rheumatologic manifestations, with a higher frequency in females. Undifferentiated rheumatoid arthritis, undifferentiated juvenile idiopathic arthritis, and Kawasaki disease were the predominant conditions. Although lower lymphocyte counts and immunoglobulin levels were observed among non-rheumatologic patients, the differences were not statistically significant. Impairments in T-cell-mediated immunity and antibody synthesis among individuals with CID hinder the recognition of autoantibody-associated rheumatologic disorders and delay diagnosis. Moreover, these conditions often present atypically in immunocompromised hosts; therefore, a vigilant clinical approach is essential for early identification and management.