Rheumatoid arthritis in an adult patient with mosaic distal 18q-, 18p- and dicentric ring chromosome 18

Ring chromosome 18 has a highly variable phenotype, depending on the extent of distal arm deletions. It is most commonly presented as a combination of 18p- and distal 18q- syndrome. IgA deficiency and autoimmune diseases have been previously described in these patients. Seven cases of juvenile rheumatoid arthritis (JRA) have been reported. Here we report the first case of late onset rheumatoid arthritis (RA) in a 32 year old Dominican woman with hypothyroidism, vitiligo, IgA deficiency, interstitial lung disease (ILD), cystic bronchiectasis, and features consistent with 18p- and distal 18q syndrome. Comparative genome hybridization analysis showed a del(18p11.21p11.32), dup(18q11.21-q22.1), and del(18q22.1-q23). Chromosomal analysis and fluorescence in situ hybridization showed three cell lines. One cell line was detected with a dicentric ring chromosome, another with duplication of the long arm and no short arm, and lastly a long arm terminal deletion of 18. The multiple autoimmune findings in our patient lends further support to the idea of loci on chromosome 18 playing a role in autoimmune disease expression. Late onset RA and ILD in a patient with chromosome 18 abnormalities are novel findings and are additional conditions to be aware of in this population.