TBA (17A183)

Down's Arthritis - Clinical and Radiological Features of arthritis in children with Trisomy 21

Author(s)

Dr Orla Killeen1

Dr Emma MacDermott1

Professor Ursula Fearon2

Professor Gerry Wilson3

Professor Douglas Veale4

Department(s)/Institutions

1.  The National Centre for Paediatric Rheumatology (NCPR), Our Lady's Children's Hospital, Crumlin (OLCHC0

2.  Trinity Biomedical Sciences Institute (TBSI), Trinity College, Dublin

3.  Conway Institute, University College Dublin (UCD)

4.  St. Vincent's University Hospital, Dublin

Introduction

DA was first reported in the literature in 1984. Crude estimates suggest higher incidence and prevalence rates of DA compared with JIA, (JIA prevalence 1/1000, estimated DA prevalence 8.7/1000).  Despite this fact, there remains a paucity of data on this condition.  DA is rarely recognised at onset & remains under-diagnosed.  As a direct consequence, children with DA are presenting with significant joint damage and disability at diagnosis.  We set up a National Musculoskeletal Screening Programme (NMSP) for children with Down syndrome (DS), age 0-21yrs, living in the Republic of Ireland.  

Aims/Background

1.  Identify whether DA is missed, leading to a delay in diagnosis

2.  Describe the clinical and radiological features of DA

Method

Children with DS were invited to attend a screening clinic. During the screening appointment, completion of a health questionnaire and a comprehensive musculoskeletal examination were performed. DA cases detected were investigated and managed as per normal clinical practice. Data on a convenience sample of 33 newly diagnosed children with JIA was collected to create a comparison group.

Results

Over an 18-month period, 550 children with DS were screened for DA (56% Male; age 0.6-19.2yrs;).  The NCPR cares for 40 children with DA, 75% of these children were detected through the NMSP.  Only 11% of these parents suspected that their child may have arthritis, and this was only after reading our recruitment literature.  Our results suggest an Irish DA point prevalence of 18-21/1000.  There was a significant delay (p<0.05) in diagnosis of DA, 1.7 years (0.2-4.9yrs) versus 0.7 years (0.2-2.4yrs) in the JIA cohort.

Children with DA were noted to have a significantly higher restricted joint count (RJC) than observed in the JIA comparison group (DA-RJC = 5 (0-12) versus JIA-RJC = 2 (0-10), p<0.05).  Small joint involvement of the hands was noted in 88% of the DA cohort, significantly higher (p<0.01) than that observed in the JIA comparison group (43%).  Erosive joint damage was higher in DA (29%) compared with JIA (10%).  These data suggest that DA is associated with greater joint damage and functional disability.  On average, in a given JIA cohort, 19% of patients would be expected to have the ILAR subtype polyarticular (pJIA) RF negative arthritis.  Based on clinical features, this is the subtype most frequently diagnosed in our DA cohort (85%), a significantly greater proportion than expected (chi square=106, df=7, p<0.0001). Methotrexate-associated nausea was a significant barrier to treatment with this DMARD in DA.

Conclusions

Our data suggests that DS is associated with a very high risk of developing polyarticular inflammatory arthritis, greater than previously reported.  There is a lack of awareness of this risk among health care professionals and the general public at large. This almost certainly contributes to poor recognition of the disease and a delay in diagnosis.  Treatment with standard protocols used in JIA is complicated by drug-associated side effects in children with DS.  However, a good response to treatment with steroid joint injections and anti-TNF therapy has been observed.  We advocate that all children with DS have an annual musculoskeletal examination as part of their health surveillance programme.