AB0956 JIA ASSOCIATED TO CHROMOSOME 18 SHORT ARM DELETION: A CASE REPORT

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Background Monosomy 18p is a rare chromosomal disease resulting from complete or partial deletion of chromosome 18 short arm. It is associated with a variable phenotypic spectrum. Most reported patients have holoprosencephaly, developmental delay, short stature and distinctive facial features while autoimmune diseases are rarely seen. Manifestations of this syndrome vary depending on the extent of deletions. Objectives We report the case of a child with juvenile arthritis and uveitis associated to 18p deletion syndrome. Methods A 5-year-old girl diagnosed with 18p deletion presented for pain and swollen joints since more than a year. She is the first born of a 51-year-old father and 40-year-old mother, non-consanguineous parents, at full term, and has a history of early hypotonia, psychomotor developmental delay and failure to thrive. Physical exam revealed arthritis of both ankles, the right knee and the MCP joint of the left thumb. We noted loose joints, high-arched palate and facial dysmorphism (hypertelorism, large protruding ears, flat nose and short philtrum). Body weight and height were at -3SD. Intellectual disability was mild. Laboratory tests showed slightly increased ESR (35mm at first hour) with positive ANA (>1/1000) and negative RF and anti-CCP. Karyotype is 46XX with deletion of the short arm of chromosome 18. Both parents had normal Karyotypes. MRI of the brain showed cortical atrophy and periventricular leucomalacia. Ophthalmic screening detected bilateral anterior uveitis. The patient was treated by AINS and methotrexate along with topical ophthalmic steroids. 6 months after treatment, the child had complete regression of uveitis and arthritis. Results This case of de-novo 18p deletion is associated to oligoarticular JIA with uveitis. According to our knowledge, there have only been 2 published cases of juvenile inflammatory arthritis with 18p deletion although 5 other cases were reported in association to other chromosome 18 abnormalities (deletion of long arm and ring). Few reports of adult-onset arthritis with monosomy 18p are available. The exact explanation of this association is still unclear. As gene loss is a major factor in the pathogenesis of inflammation, this presentation might be related to deletion of PTPN2, a gene that has been associated to rheumatoid arthritis. PTPN2 encodes Protein Tyrosine Phosphatase Non-receptor type 2 and is located in the short arm of chromosome 18. PTPN2-deficiency stimulates T follicular helper cell and B cell responses thus promoting autoimmune reaction. Of the 67 genes in 18p, only around 12 (of which PTPN-2) are responsible of a phenotype when hemizygous. Further genetic studies are needed to better elucidate the role of deleted genes in the pathogenesis of inflammation in monosomy 18p. Conclusion In addition to skeletal deformities such as kyphosis and feet deformities, children with 18p deletion should be screened for inflammatory arthritis.