Immunodeficiency and Autoimmunity: Immune Dysfunction in Chromosome 18q Deletion Syndrome – A Case Report

Chromosome 18q deletion syndrome is characterized by multiple comorbidities, some of which are defined by immune dysfunction, which will encompass the scope of the case discussion presented. The patient is a 12-year-old male, an only child of non-consanguineous parents. His prenatal care was uneventful, and his mother had a second miscarriage. He was born at term by cesarean section, weighing 3,530 g. At birth, he had a cleft lip and palate, congenital clubfoot, congenital heart disease, and global developmental delay. In his early years of life, he was frequently hospitalized for fevers of unknown origin and infections, with his first hospitalization at 3 months of age. At the age of 1 year and 5 months, a reduction in lymphocytes and immunoglobulins was observed: IgG 483.65 (<p3), IgM 33.43 (<p3), CD3 575 (<p10), CD4 386 (<p10), CD8 153 (<p10), followed by changes in thyroid hormones, indicating secondary hypothyroidism at 2 years and 5 months (thyroid-stimulating hormone 8.45 T4L 0.77). Since the diagnosis, he has been on monthly IV immunoglobulin replacement, prophylactic antibiotic therapy, and levothyroxine, showing clinical and laboratory improvement to date. Chromosome analysis of lymphocytes using the G-banding technique revealed 46 XY, der(18)t(8;18) (q24.1;q21) of paternal origin, which confers partial deletion of the long arm of chromosome 18 and partial duplication of the long arm of chromosome 8. Chromosome 18q deletion sndrome associates the deletion of certain gene loci with the prevalence of immunodeficiency and autoimmunity. In patients with a distal 18q deletion (18q21–q23), as mentioned above, hypogammaglobulinemia, defects in B cell maturation, antibody production, lymphocyte survival, cytokine signaling, and regulatory T cell homeostasis are predominant. Consequently, there is a predisposition to immunodysfunction, leading to recurrent infections characteristic of immunodeficiency and autoimmune diseases, requiring appropriate therapeutic intervention and multidisciplinary monitoring.