INTRODUCTION
Systemic juvenile idiopathic arthritis (sJIA), the least common subtype
of juvenile idiopathic arthritis (JIA), is a chronic inflammatory
disease characterized by fever, arthritis, and at least one of the
following: rash, generalized lymphadenopathy, hepatomegaly/splenomegaly,
and/or serositis 1. Compared to other subtypes of JIA,
sJIA can cause more severe systemic complications including pericarditis
and pleuritis. Pulmonary complications of sJIA such as pulmonary
hypertension, interstitial lung disease, and pulmonary alveolar
proteinosis are rare, but can cause significant morbidity and mortality2,3. Childhood interstitial lung disease (chILD) in
general is a rare and heterogenous group with prevalence ranging from
0.8 - 2.1 per million in Australia and Asia to 3.6 cases per million in
the United Kingdom and Ireland 4,5. Since the early
2010s, researchers identified an increased incidence of interstitial
lung disease (sJIA-LD) in pediatric patients with sJIA, with a 2020
cohort estimating a new prevalence of almost 7% 6.
This is a new development in the clinical presentation of sJIA, as prior
to 2000, published literature on sJIA-LD were primarily case reports7. In 1980, Athreya et al reported a rough estimate of
4% of patients with juvenile rheumatoid arthritis had pleuropulmonary
disease, but they did not describe percentage of lung disease in sJIA8. Given the high mortality rate of sJIA-LD6, researchers have attempted to identify the
pathophysiology and underlying risk factors of sJIA-LD. Identified
demographic risk factors include disease onset at less than 2 years of
age and presence of trisomy 21 2,9. Common clinical
features were minimal respiratory symptoms, lymphadenopathy,
hepatosplenomegaly, and clubbing 6,10. Radiographic
findings included septal thickening and ground glass opacities6,9.
Therapeutic management plans are complicated in children with sJIA-LD.
Some studies have identified a correlation between increased use of
anti-cytokine therapy for sJIA in the early 2010s and the increase in
sJIA-LD 6, 9, 10. However, one confounding factor is
that patients with sJIA-LD often have increased severity of systemic
symptoms, which could require increased medication exposures. For
instance, a history of macrophage activation syndrome (MAS), a
life-threatening complication of rheumatic disease, appears to be a
common finding in those with sJIA-LD, highlighting the severity of these
patients’ disease 2, 6, 10. Despite the increase in
prevalence of sJIA-LD, little is known about this disease process, and
we seek to broaden the field of knowledge on this subject. In this
single-center, retrospective case series of 9 patients, we analyzed
demographic, clinical, radiographic, and laboratory data to corroborate
common clinical characteristics and present our clinical guidelines for
diagnosis and monitoring of interstitial lung disease in children with
sJIA.