Macrophage Activation Syndrome and Lung Disease Presenting at Onset in a Child with Systemic Juvenile Idiopathic Arthritis

MAS with Lung Disease in sJIA

Abstract

Macrophage activation syndrome (MAS), a form of secondary hemophagocytic lymphohistiocytosis, is commonly encountered in pediatric rheumatologic emergencies. Recognition of MAS in a child with systemic juvenile idiopathic arthritis (sJIA) is challenging because the prominent inflammatory expression of sJIA obscures its subclinical forms. Lung disease detected in these children is characterized by a distinct immunological and clinical feature. We describe a boy aged 13 years presenting with fever for 3 months followed by polyarthralgia, maculopapular rash, non-productive cough, and constitutional symptoms including anorexia, weight loss, and generalized paleness of the body. On examination, the child had pallor, grade-1 clubbing, pedal edema, hepatomegaly, and fine crepitations in the right lower lung field. The child fulfilled Pediatric Rheumatology International Trials Organisation criteria for MAS in sJIA and was managed by pulse methylprednisolone, immunoglobulin, and cyclosporine, which showed a significant response. The child was successfully treated and discharged home. MAS in the clinical setting of sJIA is life-threatening; prompt initiation of immunosuppressive therapy can be life-saving.