Systemic juvenile idiopathic arthritis (SJIA) is increasingly being diagnosed in children with lung disease (LD), particularly among those patients with macrophage activation syndrome (MAS), according to study results published in Arthritis and Rheumatology.
The results of the study indicated that SJIA-associated LD (SJIA-LD) had distinct clinical and immunologic features, representing a currently uncharacterized type of inflammatory LD.
The study included patients with SJIA-LD (n=18). Researchers extracted clinical data from medical records and performed epidemiologic, cellular, biochemical, genomic, and transcriptional profiling analyses.
From radiographic analysis, the researchers found diffuse ground-glass opacities, subpleural reticulation, interlobular septal thickening, and lymphadenopathy. Their pathologic findings included patchy but extensive lymphoplasmacytic infiltrates and mixed features of pulmonary alveolar proteinosis (PAP) and endogenous lipoid pneumonia.
Compared with patients with SJIA and no LD, those with SJIA-LD were younger at SJIA diagnosis (odds ratio [OR], 6.5; P =.007), had prior episodes of MAS (OR, 14.5; P <.001), had prior adverse reactions to biologic therapy (OR, 13.6; P <.001), and had higher serum interleukin-18 levels (27,612 vs 5413 pg/mL; P=.047).
The researchers found that patients with SJIA-LD did not have genetic, serologic, or functional evidence of granulocyte-macrophage colony-stimulating factor-pathway dysfunction, which is usually seen in familial or autoimmune PAP. Compared with primary PAP, bronchoalveolar lavage in patients with SJIA-LD rarely demonstrated proteinaceous material and contained fewer lipid-laden microphages (66.1% vs 10.5%; P <.0001).
“[T]hese observations underscore the critical need for well-designed multicenter epidemiologic studies including different geographic areas with different patterns of medication utilization to define risk factors and support strategies to prevent development of this disorder,” the researchers wrote.