Abstract
Rheumatological diseases are non-preventable diseases of chronic inflammation which can involve multiple joints and/or organs. The causes of these diseases are unknown but are believed to involve both genetic and environmental factors. Rheumatological diseases are a diverse group including juvenile idiopathic arthritis (JIA), dermatomyositis, Kawasaki disease, and systemic lupus erythematosus (SLE). Together these four conditions diseases account for around 75% of all hospitalisations for rheumatological conditions in 0–24-year-olds in Aotearoa. As chronic diseases, often characterised by pain, fatigue and loss of mobility, they can have wide-reaching effects on physical, mental, and social well-being. In some instances, for example, systemic onset JIA, Kawasaki disease (which can damage the heart) and SLE (which can damage the kidneys or affect the brain),or Macrophage Activation Syndrome (in any of these conditions) untreated disease can be life-threatening.
JIA is the most common rheumatologic condition among New Zealand children and adolescents overall, with an incidence of 5 per 100,000 per year and it accounts for nearly half of all rheumatological hospitalisations. However, in children under 5 years, Kawasaki disease is the most common, with an incidence of 8 per100,000 per year.
Although the number of individual children hospitalised with rheumatological disease per head of population has changed little over time, the total hospitalisation rate has been increasing because the number of hospitalisations per individual has been steadily increasing, especially since 2014. The mean length of hospital stay has decreased, from over 3 days in 2004 to less than one day in 2022. These changes most likely to reflect changes in recommended treatment, specifically regular (biologic) infusions. Over the 5 years 2018 to 2022, individuals with these diseases were hospitalised, on average, 3 times each.
Hospitalisation rates have increased over time in all except the youngest (0–4 years) age groups and in all the larger ethnic groups. Pacific children and young people have generally had a considerably higher hospitalisation rate than Māori or European/Other children. In most years from 2000 to 2020, hospitalisation rates children in the most deprived areas (quintile five) were markedly higher than the rates for children in the other four quintiles but in recent years this gap has narrowed. Hospitalisation rates peak in the early teenage years. Females have significantly higher admission rates than males, reflecting the higher prevalence of JIA and SLE in females.
The various rheumatological conditions have different demographic patterns. JIA has the highest hospitalisation rates in European/Other children whereas Kawasaki disease disproportionately affects young Asian/Indian children. Although not reflected in these data, there are recent reports of very high rates in Pacific children. SLE has the highest rates in Pacific adolescent and young adult women and gout affects almost exclusively Pacific young men. Without adjustment for the different prevalences of these diseases in the different ethnic groups in the population (which likely have a genetic basis), and the differences in how the different ethnic groups are distributed across deprivation quintiles, it is difficult to determine the degree to which any differences in hospitalisation rates by level of deprivation may be influenced by disparities in socioeconomic resources or access to healthcare between deprivation quintiles.
Because rheumatological diseases often involve multiple organ systems and have profound impacts on many aspects of a patient’s life, guidelines commonly recommend care by a multi-disciplinary team including a rheumatologist (and other medical specialists such as an intensive care specialist, ophthalmologist, nephrologist, neurologist, cardiologist, orthopaedic surgeon or dermatologist, depending on the organ systems involved in the disease), nurse specialist, physiotherapist, occupational therapist, and psychologist. Whilst there is reasonable evidence in regard to the treatment of the four main rheumatological diseases in children, some evidence for medical treatment in paediatric rheumatology conditions (especially the rarer conditions) is derived from adult trials. Treatment for rheumatological diseases in children can be complex and associated with unpleasant side-effects which further adds to the psycho-social impact of these conditions.
Drugs available for treating JIA include non-steroidal anti-inflammatory drugs (NSAIDs), systemic and intraarticular glucocorticoids, and non-biologic and biologic disease modifying antirheumatic drugs (DMARDs). Emerging evidence suggests early aggressive treatment is preferable to “stepwise” therapy.
Prompt diagnosis and treatment of children with Kawasaki Disease is vital because, without treatment, around a quarter of patients develop coronary artery aneurysms. All children with suspected juvenile dermatomyositis or Kawasaki disease should be referred to a specialist centre urgently. Children with SLE tend to have more severe disease than adults and require frequent outpatient follow-up.
Half of all hospitalisations with a primary diagnosis of rheumatological disease are of children and young people who live in the Northern region. Districts with hospitalisation rates significantly higher than the national average are Waitematā, Auckland, Bay of Plenty, Lakes, Hutt Valley, and Wairarapa.
The Ministry of Health funds the New Zealand Paediatric Rheumatology Service to provide care for children with rheumatological conditions. However, international estimates suggest that the service is significantly under-resourced for the New Zealand population with a very small team providing services across the country.