Primary antibody deficiency associated with ring chromosome 18

Abstract

Background: Patients with chromosome 18 abnormalities can present with an immune phenotype that resembles common variable immunodeficiency. Knowledge of the genes underlying the immune defects related to chromosome 18 aberrations could improve our understanding of the molecular basis of primary antibody deficiencies. Here we present a patient with ring chromosome 18 affected by primary antibody deficiency and autoimmunity. Methods: Lymphocyte populations were determined by flow cytometry. Specific antibody response to protein vaccines and pneumococcal capsule antigen were measured by ELISA. Genome sequencing was performed using a PCR-free protocol. Case: The patient was diagnosed with ring chromosome 18 for delayed growth and dysmorphic features at the age of 1 month. Array comparative genomic hybridization showed deletions of 18p11.21-pter and 18q21.31-qter. At the age of 10 months, she started having recurrent episodes of otitis media and pneumonia, as well as autoimmune arthritis. Serum immunoglobulins and specific antibody levels were low. The CD19+CD27+ memory B cell and CD45RO+ T cell populations were decreased. Recurrent infections were controlled with parenteral immunoglobulin and autoimmune arthritis was treated with systemic and intra-articular therapies. Conclusions: Selective IgA deficiency is the most common form of immunodeficiency associated with chromosome 18 abnormalities, however patients with ring chromosome 18 may also be affected by specific antibody deficiency and require immunoglobulin replacement for optimal care. These patients might partially share the same genomic loss as in patients with non-syndromic primary antibody deficiency. Statement of novelty: This report highlights an important teaching point about immune deficiency in a chromosomal anomaly that is not infrequently encountered in pediatric hospitals. Furthermore, our investigations provide more insight into the pathogenesis of immunodeficiency among patients with chromosome 18 abnormalities.