Version July 2025
AEC: absolute eosinophil count; BAL: bronchoalveolar lavage; CT: computed tomography; CXCL9: C-X-C motif chemokine ligand 9; DLCO: diffusing capacity for carbon monoxide; HLA: human leukocyte antigen; IL: interleukin; MAS: macrophage activation syndrome; PFTs; pulmonary function testing; sIL-2R: soluble IL-2 receptor; sJIA: systemic juvenile idiopathic arthritis; sJIA-LD: sJIA-associated lung disease.
¶ High disease activity includes having ≥1 episode of MAS, elevated biomarkers of MAS (ie, CXCL9, IL-18, ferritin, sIL-2R), and/or requiring intensive care. Suggestive features of MAS include unremitting fever and rash, hepatic dysfunction, and/or extremely high serum ferritin. For more information on the diagnosis of MAS, refer to UpToDate content on complications of sJIA.
Δ Evidence of lung disease may include abnormal vital signs (ie, respiratory rate and/or oxygen saturation), lung examination (eg, crackles), cyanosis, and/or clubbing.
◊ Having a negative test for HLA DRB1*15:XX does not exclude the possibility of having SJIA-LD.
§ In patients with a baseline AEC of ≤500/microL, eosinophilia is defined as having two consecutive AEC >500/microL separated by at least 1 week. Otherwise, in patients with a baseline AEC of >500 /microL, eosinophilia is defined as having 2 consecutive values over twice the baseline value.
¥ PFTs should include spirometry, lung volumes, DLCO, and a 6-minute walk test. If the patent is too young to obtain PFTs, they can do a 3-minute walk test.
‡ sJIA disease activity is considered controlled if the patient's symptoms and disease-related biomarkers have improved as expected with therapy. Patients who do not have abnormalities identified on initial pulmonary evaluation but who do have refractory sJIA disease activity still require additional pulmonary evaluation.
† BAL should be performed for new pulmonary findings on chest CT and/or concern for a lower respiratory tract infection as an alternative or concomitant diagnosis, especially in severely immunocompromised patients.
** Refer to UpToDate content on the treatment of sJIA and sJIA-LD.
