General Medicine Advanced Trainee at Greenslopes Private hospital
An Unusual Case Of Adult Onset Still’s Disease
To report a rare case of Adult onset Still’s disease associated with reactive MAS that fulfils the ACR/EULAR proposed classification criteria for reactive MAS
A 60 year old male, with no significant past medical history, presented with a 4 week history of myalgias, arthralgias, lethargy and weight loss. His initial laboratory tests showed a positive ANA and a mildly positive rheumatoid factor with negative anti CCP. He was diagnosed as rhupus and discharged with oral methotrexate and weaning doses of prednisolone. The patient had stopped this in the community. A few months later, he presented with high fever associated with an erythematous rash. He was pancytopenic with high markers of inflammation and a low C3. He was thoroughly investigated and all other causes such as infections, autoimmune rheumatic diseases and malignancy were excluded. He was discharged when he presented to the hospital 3rd time after a few weeks with similar symptoms and pancytopenia. A consultant rheumatologist and immunologist opinion was sought during all admissions. He had an elevated ferritin 1420 microg/L. He was diagnosed with AOSD, though fulfilling only 3 major criteria from Yamaguchi diagnostic criteria. He also had fibrinogen 2.51 g/L and platelet count of 104 on presentation. This meets the ACR/ELAR criteria for reactive MAS. He was commenced on IV Methylprednisolone, Hydroxychloroquine and Leflunomide, resulting in a marked improvement of his symptoms and normalization of serum inflammatory markers.
This case highlights the challenging diagnosis of AOSD complicated with MAS. The diagnosis was challenging due to the concurrent presentation of MAS.
AOSD complicated by MAS remains a complex disorder challenging in diagnosis and treatment. Reported rates of occurrence of MAS in patients with AOSD vary from 12% to 56%.
AOSD- Adult onset Still’s disease
MAS- Macrophage activation syndrome
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