Department of Rheumatology, Alder Hey Children's Hospital, Eaton Road, Liverpool and
1 Department of Paediatrics, Countess of Chester Hospital, Chester, UK
SIR, Arthritis associated with Down syndrome (trisomy 21) has been described in previous studies [15]. Myth, anecdotes and rumour have suggested that the prevalence of arthritis is higher in children with Down syndrome. We wanted to estimate the prevalence of arthritis in our population of children with Down syndrome to see if there is any evidence to support this anecdote.
We have identified four children with Down syndrome and presenting with arthritis in the last 22 yr in the Mersey region (Royal Liverpool Children's Hospital, Alder Hey and all the neighbouring district general hospitals in the Mersey region). The case notes of these patients were reviewed for data collection. In total there were four patients with Down syndrome and arthritis in the last 22 yr in the Mersey region (Table 1). Three were females. All patients had full blood counts checked as part of the initial screen to exclude leukaemia, and none have developed this disease subsequently.
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The total number of children with Down syndrome in England and Wales between 1978 and 1990 was 6068 (data obtained from Office of Population Census and Surveys). The national incidence rate of children born with Down syndrome during the same period ranged between 5.9 and 8.4 per 10 000 live births (median 7.2/10 000). The total number of live births in the Mersey region during these 13 yr was 390 000 (data from Mersey Registry). Using the national median incidence rate of 7.2/10 000 live births, the number of cases of Down syndrome in the Mersey region during the period 19781990 was estimated to be 280 (7.2/10 000 x 390 000). The number of children born with Down syndrome between 1990 and 2000 in the Mersey region was 278. Data were taken from the Confidential Enquiries into Stillbirths and Deaths in Infancy (CESDI) registry.
The total number of liveborn children with Down syndrome during the study period was therefore 558. The annual incidence rate of arthritis in Down syndrome using the above data, calculated as 558 x 100 000/22, shows the rate to be 33/100 000/yr, which is higher than that the incidence of juvenile idiopathic arthritis in the general population (10/100 000/yr) [6].
We acknowledge that the number of patients studied is small and that this is only a crude estimate. Three out of the four patients presented with arthritis before 5 yr of age. If the population of children with Down syndrome is divided into 5-yr cohorts, the children born after 1995 could still in theory develop arthritis. Therefore our figure of 33/100 000/yr may well be an underestimate of the incidence of arthritis.
Children with Down syndrome have unusual hand shapes and joint hypermobility and this sometimes leads the inexperienced to miss active arthropathy. This study suggests that arthritis is more common in children with Down syndrome, confirming what has been anecdotal for many years. Further studies using larger numbers will be required to confirm this.
Notes
Correspondence to: B. Padmakumar, The Royal Oldham Hospital, Rochdale Road, Oldham OL1 2JH, UK.
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