Case Presentation: A 24 yo male with a history of juvenile idiopathic arthritis ( JIA), macrophage activation syndrome (MAS), and pyoderma gangrenosum presented with fever to 102.9F and rash for 2 days. He had a diffuse, erythematous, un-raised, itchy rash which started on his arms and spread to his chest and back. He had recently been started on dapsone 10 days prior for management of his pyoderma gangrenosum. He was supposed to be on IVIG, but due to insurance reasons could not receive it. This caused a worsening of his disease. He was diagnosed with JIA as a child, and had his first episode of MAS at 5 years old. Since then, he has had multiple episodes that typically present with fever, rash, and fatigue. A year ago, he was diagnosed with pyoderma gangrenosum, and has had multiple sores since then. Dermatology and rheumatology were consulted from the beginning, and labs were significant for a low white blood cell count, hemoglobin, and platelet count, and elevated ferritin level and AST. He was started empirically on antibiotics, however after further testing these were discontinued because there were no clear signs of infection. He was diagnosed with an MAS flare most likely triggered by the dapsone, and started on an IV burst of methylprednisone for three days. He was discharged in a stable condition with plan to continue his current rheumatologic regimen of Anakinra, and his PO steroids at discharge. He also received 2 doses of IVIG to help with his pyoderma gangrenosum while he was inpatient.
Discussion: We report a challenging case of MAS and pyoderma gangrenosum in a patient with a history of JIA. MAS is a rare syndrome of unknown incidence and variable clinical presentation that can be difficult to diagnose early. It can be triggered by bacterial and viral infections, or even new medications. MAS can cause spontaneous bleeding, bruising, hepatic dysfunction, lethargy, seizures, coma, or shock. Diagnostic criteria include elevated ferritin, fever, low platelet count, and elevated AST. There is a 10% association of acquired MAS with systemic onset JIA. In fact, MAS is a poor prognostic factor that significantly increases mortality in JIA patients. More research is needed to determine optimal treatment for patients with this condition, but most studies recommend high dose steroids and immunosuppression. Although pyoderma gangrenosum is not associated with MAS, and is more likely to be associated with JIA, 25% of MAS patients present with some form of skin lesion. Interestingly, pyoderma gangrenosum is also uncommon, with an incidence of 3-10 affected per million people.
Conclusions: Macrophage activation syndrome is a rare and life-threatening complication of juvenile idiopathic arthritis requiring aggressive therapy due to multiple organ involvement. The diagnosis and treatment is challenging and needs early recognition. Further research needs to be done to determine optimal treatment for patients with this condition. This case is reported to increase awareness for a unique presentation of MAS.