043. Radiological features identified in the hands of children with Down syndrome and inflammatory arthritis

Abstract

Background: Down's arthritis (DA) is an inflammatory joint condition affecting children with Down syndrome. It is 18-21 times more common than juvenile idiopathic arthritis (JIA) in the general paediatric population (JIA prevalence 1/1000). Children with DA present with a poly-articular (5 or more joints), Rheumatoid Factor (RF) negative pattern of disease, with predominance in the small joints of the hands and wrists. Despite it's higher prevalence, a significant delay in diagnosis is frequently observed. Joint laxity and hypotonia are almost universal in children with Down syndrome, contributing to an increased risk of a number of musculoskeletal disorders and degenerative joint disease. Clinical signs and symptoms may not always help differentiate between inflammatory joint disease and joint hypermobility. Aims: We aim to report the radiological features described by a Paediatric Musculoskeletal Radiologist (PMR) when reviewing hand and wrist radiographs in a cohort of children with DA. Methods: A retrospective review of all hand and wrist radiographs in a convenience sample of 19 children with DA was undertaken by a PMR. Bone age, carpal and metacarpal bone abnormalities were documented, as were corresponding clinical findings following musculoskeletal examination by a Paediatric Rheumatologist. Wrist MRIs were performed on 4 of the 19 children. The results of these studies were also included in our report. Results: Eighteen of the 19 children (10/19 (53%) Female; Average Age 13yrs, range 0.8-19yrs; 100% Full Trisomy 21 genetics) had radiographs of their hands and wrists. Bone age was below chronological age in 5 (28%) of the cohort imaged. Time from symptom onset to DA diagnosis was known in 8/19 children and on average was 1.8 years (0.14-4.9 years). Over half (63%) of the cohort were detected through a musculoskeletal screening programme offered to children with Down syndrome and not from direct referral to the tertiary rheumatology centre. On musculoskeletal examination the most commonly affected joints, 95% of cases, were the proximal-inter-phalangeal joints (PIPs), followed by the wrists (68%), knees (58%), toes (37%) and metacarpal-phalangeal joints (MCPs) (32%). The average joint hypermobility score using the Beighton system was 2 (0-6). Radiograph and MRI review highlighted a range of carpal and metacarpal bone abnormalities. The most common abnormality was crowding of the carpal bones with associated degenerative disease (63%). The earliest sign of degenerative disease was observed in a child aged 10 months whose MRI with gadolinium contrast demonstrated synovial enhancement of the proximal carpal row. The second most common finding (42%) was scalloping of the base of the first metacarpal. Other less frequent features identified (5% of cohort) included carpal pits, tuft irregularity and dactylitis. Alarmingly, 50% of the cohort had evidence of bone erosions on plain film. Conclusions: Radiographic carpal and metacarpal bone changes appear to be prevalent in DA and do not always correspond to clinical signs and symptoms. Undetected, these features can cause significant and widespread and functional impact. If detected and managed in a timely and appropriate manner, irreversible joint damage and longterm sequelae could be avoided. These results support the importance of access to a specialist musculoskeletal Radiologist and MRI. Our next steps will include comparison of these results with two separate cohorts; children with JIA and children with Down syndrome with no evidence of inflammatory arthritis.